I am relatively new to dnd and am planning to run one of the WotC prewritten adventures, but I don't which adventure to pick. I've heard that Curse of Strahd is the best of the prewritten adventures, but I'm worried that the module might be harder for a new DM. I'm willing to put time into preparing games, but want to avoid anything too complex. Which prewritten adventure should I run?

I cannot positively recommend any adventures, but I would recommend against Icewind Dale and Descent into Avernus.  

Icewind Dale is incredibly thin in its plot, with a poorly articulated BBEG and unacceptable pacing issues (which I will not spoil here, but it is really, really bad).  The setting itself is not bad and it has some decent building blocks... but the campaign requires a DM who is willing to basically toss out large portions of the prewritten campaign and supplement the portions which are rather thin.  

Descent into Avernus is little more than a glorified fetch quest.  Its story is extremely linear and not overly interesting, and tries to rely on gimmicks in order to make the campaign seem unique.  This is another one where a DM has to do a lot of heavy lifting if they want to make something enjoyable, working better as a starting point rather on which to build a more detailed campaign.  

It really depends on taste. What genre are you after? What kind of style game do you want to run? The different adventures are mostly differentiated according to taste rather by any other metric. Strahd is a horror with vampires etc. If that's up your alley, crack on. Otherwise, let us know what kind of things you enjoy (genre, combat v roleplay, narrative v sandbox, etc), and maybe we can think of an adventure that will suit you. Just don't get Spelljammer, far too little for a premium price.

I've never run a large published adventure, but I have used a lot of the modular adventure anthologies (Tales from the Yawning Portal, Candlekeep Mysteries, Radiant Citadel, etc) and if you're not sure you want to commit to a whole Strahd-sized adventure, they're a great alternative. 

Some of them (like Candlekeep) you can run as a campaign, but mostly I like to pick pieces of them out to use to populate my existing plot and game world. It gives you slightly more freedom without still having to do all the prep work.

I would recommend checking out THIS guide by ArcaneEye on prewritten modules. To be honest, there are a lot of decent adventures out there and what you would like best will definitely depend on how much work you want to do, what style or theme your players want, and how challenging you want the game to be.

However, I will say that Keys From the Golden Vault is quite good if your players are into heists and adventures that revolve more around being sneaky than fighting stuff. Candlekeep Mysteries, Journeys Through the Radiant Citadel, Lost Mine of Phandelver, Waterdeep Dragon Heist, and Call of the Netherdeep are all books that I have either looked over or run some of and they all seemed good to me.

I would probably avoid Dungeon of the Mad Mage, the Strixhaven adventure book, and Storm King's Thunder. However, some people have liked those books though the former is very combat heavy, the second book mentioned is incomplete, and the latter requires a lot of work and isn't designed very well.

I haven't played or seen Curse of Strahd, but I have heard that it is both difficult to run but also quite fun. It makes sense to be hesitant about DMing it though if you don't want to experience a high level of difficulty.

Basically, there are a lot of choices and what is best really depends on a ton of different factors. Pick what you think is best for you and your group, us random people on the internet can only help you so much.

I recommend investing in a pad of graph paper and making your own.  

Lost Mine of Phandelver, Dragon of Icespire Peak, and Dragons of Stormwreck Isle are all intended for new DMs and new players.  They are a great way to start the DnD journey, and their scope is modest enough that it does not feel overwhelming from the outset.  I know there are some resources out there for how to combine Lost Mine and Icespire Peak if you want more content since both are set in the same area.

Dragons of Stormwreck Isle is designed to get characters to lvl 3.  If you want to use Curse of Strahd that is the "real" starting point for the adventure anyway if I recall correctly.  You could do Stormwreck Isle to cut your DMing teeth then be in a good spot to begin Curse of Strahd if the Gothic horror theme appeals to you and your players.

I also agree with the suggestion that the anthology collections can be a nice way to pick and choose more bite-sized adventures to run.

Quote from Dragonmage77 >>

I am relatively new to dnd and am planning to run one of the WotC prewritten adventures, but I don't which adventure to pick. I've heard that Curse of Strahd is the best of the prewritten adventures, but I'm worried that the module might be harder for a new DM. I'm willing to put time into preparing games, but want to avoid anything too complex. Which prewritten adventure should I run?

 Before you give up on Strahd, be aware that as the most popular adventure in 5e, it has MASSIVE support that’s been written for it, including Reddit Threads (there’s two I can think of that are practically books to themselves), as well as a number of pre-created maps.  I can’t recall everything I used myself, BUT: if you want to give it a try and you’re players have either never played it or are happy to give it another go, myself and a lot of users here can give you advice.  Be aware that as a Gothic Horror Adventure, it is very unlike what most would consider a classic D&D Adventure.  An irony as it is 5e’s best.

Edit: Also, Death House is the default introduction to Strahd.  It comes with the adventure and while it’s not very good, it’s serviceable.  For myself, I *highly* recommend The House of Lament from Van Richten’s Guide to Ravenloft.

Quote from Appellion >>

Quote from Dragonmage77 >>

I am relatively new to dnd and am planning to run one of the WotC prewritten adventures, but I don't which adventure to pick. I've heard that Curse of Strahd is the best of the prewritten adventures, but I'm worried that the module might be harder for a new DM. I'm willing to put time into preparing games, but want to avoid anything too complex. Which prewritten adventure should I run?

 Before you give up on Strahd, be aware that as the most popular adventure in 5e, it has MASSIVE support that’s been written for it, including Reddit Threads (there’s two I can think of that are practically books to themselves), as well as a number of pre-created maps.  I can’t recall everything I used myself, BUT: if you want to give it a try and you’re players have either never played it or are happy to give it another go, myself and a lot of users here can give you advice.  Be aware that as a Gothic Horror Adventure, it is very unlike what most would consider a classic D&D Adventure.  An irony as it is 5e’s best.

Edit: Also, Death House is the default introduction to Strahd.  It comes with the adventure and while it’s not very good, it’s serviceable.  For myself, I *highly* recommend The House of Lament from Van Richten’s Guide to Ravenloft.

 I'll second House of Lament as my preferred way to start Strahd vs Death House if you want to go Gothic horror from level 1.

https://www.dndbeyond.com/campaigns/premade

Someone posted this in another thread earlier - I didn't know it was available for free.
Played and DM'd it and in 5e I've DM'd Tomb of Annihilation + well into Rime of the Frostmaiden.

Tomb's a test for a DM - not sure I succeeded ;)
Rime is a mess, as has been said - not terribly well put together, bad plot etc. etc. but it's coincided with me liking the flavour and having the time to re-write (and the urge to), but it's a big job and I'm retired and would pretty much take any Campaign as something to put my own stamp/spin on, so...  it's more a "retirement project"/time filler for me and a "luxury hobby".

If you don't have stacks of time/experience I'd go with one of the shorter, everyone's recommending either collections - that you can put together as parts of a campaign - you don't need a stack of experience for that, just imagination and some story telling ability...  I'd also suggest Ghosts of Saltmarsh worth a look too and out of the Collections Versus Phandelver (or Stormwreck maybe), go with whichever of those grasps your imagination - because you're entitled to fun as well as your players.

It's free so, for my money...  Phandelver's well put together and organised logically.  Easy to prep sessions etc. etc. I wish all the modules were this well put together.  Even if you don't want to play it, it's worth getting at that price just to see what something well put together looks like.

Anyway... +1 for Phandelver

I want to thank everyone who replied; all of the responses here were really helpful! After reading these posts; I plan to run LMoP, and possibly run Dragon Heist or Call of the Netherdeep. I'm really intrested in running Tomb, but I want to at least familiarize myself with the rules by running LMoP first.

Quote from BoringBard >>

I would recommend checking out THIS guide by ArcaneEye on prewritten modules. To be honest, there are a lot of decent adventures out there and what you would like best will definitely depend on how much work you want to do, what style or theme your players want, and how challenging you want the game to be.

However, I will say that Keys From the Golden Vault is quite good if your players are into heists and adventures that revolve more around being sneaky than fighting stuff. Candlekeep Mysteries, Journeys Through the Radiant Citadel, Lost Mine of Phandelver, Waterdeep Dragon Heist, and Call of the Netherdeep are all books that I have either looked over or run some of and they all seemed good to me.

I would probably avoid Dungeon of the Mad Mage, the Strixhaven adventure book, and Storm King's Thunder. However, some people have liked those books though the former is very combat heavy, the second book mentioned is incomplete, and the latter requires a lot of work and isn't designed very well.

I haven't played or seen Curse of Strahd, but I have heard that it is both difficult to run but also quite fun. It makes sense to be hesitant about DMing it though if you don't want to experience a high level of difficulty.

Basically, there are a lot of choices and what is best really depends on a ton of different factors. Pick what you think is best for you and your group, us random people on the internet can only help you so much.

 Thanks; the link was a huge help, and I appreciate you taking the time to help a clueless wannabe DM.

Quote from Jokei >>

https://www.dndbeyond.com/campaigns/premade

Someone posted this in another thread earlier - I didn't know it was available for free.
Played and DM'd it and in 5e I've DM'd Tomb of Annihilation + well into Rime of the Frostmaiden.

Tomb's a test for a DM - not sure I succeeded ;)
Rime is a mess, as has been said - not terribly well put together, bad plot etc. etc. but it's coincided with me liking the flavour and having the time to re-write (and the urge to), but it's a big job and I'm retired and would pretty much take any Campaign as something to put my own stamp/spin on, so...  it's more a "retirement project"/time filler for me and a "luxury hobby".

If you don't have stacks of time/experience I'd go with one of the shorter, everyone's recommending either collections - that you can put together as parts of a campaign - you don't need a stack of experience for that, just imagination and some story telling ability...  I'd also suggest Ghosts of Saltmarsh worth a look too and out of the Collections Versus Phandelver (or Stormwreck maybe), go with whichever of those grasps your imagination - because you're entitled to fun as well as your players.

It's free so, for my money...  Phandelver's well put together and organised logically.  Easy to prep sessions etc. etc. I wish all the modules were this well put together.  Even if you don't want to play it, it's worth getting at that price just to see what something well put together looks like.

Anyway... +1 for Phandelver

 Thanks; I'm planning run LMoP in a few weeks.

Quote from Appellion >>

Quote from Dragonmage77 >>

I am relatively new to dnd and am planning to run one of the WotC prewritten adventures, but I don't which adventure to pick. I've heard that Curse of Strahd is the best of the prewritten adventures, but I'm worried that the module might be harder for a new DM. I'm willing to put time into preparing games, but want to avoid anything too complex. Which prewritten adventure should I run?

 Before you give up on Strahd, be aware that as the most popular adventure in 5e, it has MASSIVE support that’s been written for it, including Reddit Threads (there’s two I can think of that are practically books to themselves), as well as a number of pre-created maps.  I can’t recall everything I used myself, BUT: if you want to give it a try and you’re players have either never played it or are happy to give it another go, myself and a lot of users here can give you advice.  Be aware that as a Gothic Horror Adventure, it is very unlike what most would consider a classic D&D Adventure.  An irony as it is 5e’s best.

Edit: Also, Death House is the default introduction to Strahd.  It comes with the adventure and while it’s not very good, it’s serviceable.  For myself, I *highly* recommend The House of Lament from Van Richten’s Guide to Ravenloft.

 Thanks; I'll definitely consider Van Richten's if I end up of running CoS.