For my Tiefling warlock character, I can't decide between Hellish Rebuke and Burning Hands for a level one spell. Hellish Rebuke has a larger AoE, but requires you to take damage to use it while Burning Hands can be used instantly, but only works up close. Should I go with the Hellish Rebuke's wide range or Burning Hands' ease of use?

Personally I like Hellish Rebuke, it has slightly higher average damage (11 compared to 10.5) and it’s a reaction so would be more damage on top of what you do on your action. And you’re going to get hit at some point so why not punish them for it. 

The perk of Hellish Rebuke is that it is a Reaction, which means that it can interrupt an opponent with multiple attacks, or trigger a concentration check from a caster in the same round that a spell is cast... among other benefits.

The perk of Burning Hands is obviously a small AOE effect. As Lyxen said, it can be hard to use safely when your allies are engaged in melee, but if you are a Hexblade Warlock then you might be the first one into the fray anyway.

Generally speaking, Warlocks already have access to Eldritch Blast, which turns into a decent cantrip "AOE" as it progresses. Your limited spell slots will usually be better spent on encounter tipping spells, rather than bumping up your round by round damage. I'd recommend making a decision based on group composition. If you already have a Wizard or Sorcerer in your group, AOE damage is probably less important for you personally.

You might be right. Considering warlocks aren't suited for close-range combat, Hellish Rebuke would probably be more advantageous.

I've found Burning Hands at low levels to be incredibly effective for a Warlock.  EB works great from a range, but I was finding often that critters get within 5 feet more than I'd like.  The other thing to note is that it is a low level AoE spell, which Warlocks get few of.  And at the early levels that 3d6 is going to kill just about anything that fails a save.  At 4th level I still plan on keeping burning Hands in the list.  If you play with minis or a VTT it is not hard to keep you allies out of the way with a small pivot.

Hellish Rebuke is only OK if you are a melee focused Warlock.  (Or a multi-classer.)

Baically, pure warlocks get 1-4 spell slots per short rest and can only know 2-15 spells.  Both of them become precious.  From levels 1-5 you can not afford to waste a spell known on something that might happen.   Spells known have to be definitely be used every day.   And each spell slot used should be worth it.   HR is high damage, high range, but has a low chance of being used unless you the guy in melee. 

Which means that you should only memorize a single shot reaction to being hit spell if you are in melee combat and will be hit.

Multi-classers are different because they can use any spell slot to cast it, and they know many more spells.   For them, Hellish Rebuke is a great spell, particularly as it upcasts well (+1d10).

Quote from Mog_Dracov >>

 

Multi-classers are different because they can use any spell slot to cast it, and they know many more spells.   For them, Hellish Rebuke is a great spell, particularly as it upcasts well (+1d10).

 

 WHich is kind of funny, since Warlock is the only class that gets Hellish Rebuke (I think some subclasses get access to it as well). Although getting it as a Tiefling is fun as well, except the Tiefling version is a lot more limited. Honestly, Hellish Rebuke is a much nastier spell for people who get access to a lot of spell slots... I think it's kind of balanced under the assumption that, unless you put some effort into it, it's hard to be able to cast it very often.

I like Hellish Rebuke because it lets you deal damage on another creatures turn as a reaction spell. It helps with the action economy for you. But if you don’t get attacked very often then you won’t end up using this. 

Quote from Ajexton >>

I like Hellish Rebuke because it lets you deal damage on another creatures turn as a reaction spell. It helps with the action economy for you. But if you don’t get attacked very often then you won’t end up using this. 

 As long as you get attacked often enough to use up all your level 1 spell slots it doesn't have to be often :-)

Remember this is on a Warlock - who don't get that many slots - and they scale. So personally I wouldn't take either.

Hellish rebuke is a reaction, iirc, so if you are in the habit of taking damage, that would be my choice. 

Would say that the choice also depends on the what tiefling bloodline and which warlock subclass of the character... Standard tiefling already has the innate ability to cast hellish rebuke as a 2nd-level spell albeit once per day, so it may be redundant to have one of your few known spells be hellish rebuke as well. Similarly, if you're playing more of a "ranged attack" or "spell-slinging" type of warlock, then you might not need to cast hellish rebuke multiple times per day.

Personally, I would take burning hands for the AoE benefits that you wouldn't get from many of your other spells. Unless you have a bunch of spellcasters using AoE spells, it never hurts to be able to damage multiple targets with one casting. Frustrating when it's the swarm of mosquitos that are killing you versus the elephant.

Or, if you're allowed to use the tiefling variants from MToF, you can use the Legacy of Cania option. This variant would give you the ability to cast burning hands as a 2nd-level spell once per day instead of hellish rebuke. Then you could take hellish rebuke as a warlock spell that can potentially be cast multiple times per day. If you anticipate being hurt often enough times per game day, then it might warrant having hellish rebuke more available and the AoE benefit of burning hands is there once per day for that moment that a small mob needs to be shown the true power of your warlock.

Quote from Javier_Phenergan >>

Or, if you're allowed to use the tiefling variants from MToF, you can use the Legacy of Cania option. This variant would give you the ability to cast burning hands as a 2nd-level spell once per day instead of hellish rebuke. Then you could take hellish rebuke as a warlock spell that can potentially be cast multiple times per day. If you anticipate being hurt often enough times per game day, then it might warrant having hellish rebuke more available and the AoE benefit of burning hands is there once per day for that moment that a small mob needs to be shown the true power of your warlock.

 This is a good option if the DM allows it.  I'm surprised there isn't more love for Burning Hands.  At the early levels, 3d6 damage with AoE capability is an encounter breaker.