Hi folks, I'd really appreciate some feedback from other seasoned players and DMs on a question I have. I've got a new PC built up for a new campaign my DM is running (based in Thay, and just after the moment our now level 9 characters have freed all of Thay from slavery). Here he is: https://ddb.ac/characters/44904394/eXUKY3

One aspect of this PC is I want it to be difficult for him to lose concentration while a spell is active because for most of the time during battle it will be considering he is a Ranger whose spells are almost always Bonus Actions that require concentration. Bascially I want him to be doing damage always with that additional "Oomph" factor whether it be due to Zephyr Strike, Lightning Arrow, or others I have. I can't exactly do that if he's losing concentration from one attack.

I'm leaning toward taking Resilient (Con) over War Caster because the extra +1 Con rounds out my score to 16 which grants me that extra 8 HP, and it boosts my Con saving throw to +7 thanks to my proficiency bonus. Another pro is the Con boost is for all Con saving throws, not just ones involving retaining concentration. The downside is I don't get advantage on Con saving throws.

That's the pro with War Caster: no matter what, I always get two rolls which, I think, mathematically, is better than my +7 Con saving throw with one roll. Other pros include being able to cast a spell as a Reaction when an enemy is within melee range and provokes Opportunity Attack - but that's exactly a con in my case, too, since my PC doesn't have any spells that fit the requirement "must have a casting time of 1 action and must target only that creature" because Ranger spells are almost always Bonus Actions that take advantage of their Action slot.

This raises a fair point: should I get War Caster anyway and either trade one Bonus Action spell for a spell that fits the requirement? Or just add a spell when I level up? Going this route would also make use of my non-existent Reactions (I only have the standard Opportunity Attack).

 Looking at the link you seem to have made your decision.

Advantage on a roll is never better than a +5 and often less. For example if you have a +8 to con saves getting a +1 item would guarantee you always make a DC10 con save (from less than 20 damage) while getting advantage you would only reduce the odds from 1/20 to 1/400. Therefore as you have +4  proficiency resiliant will make you better and you round up your con the +5 to con saves resiliant gives you well make you more success at maintaining concwentration than warcaster, as your proficiency bonus improves this will get better. As you mentioned it also helps for things like poison effects

The advantage or warcaster over resiliant is its other two features.  You can cast a spell as an opportunity attack and you do not need a hand free to carry out the somantic component of spells. epending on your play style these can be huge or no big deal. (for example a sword and board ranger would have to sheather his sword as his object interaction before casting a spell and would then have to end his turn with his sword still sheathed (op attacks would have to be unarmed). 

Yeah, I was already leaning toward Resilient w/ Constitution. And though the PC uses spells, the way he uses them doesn't lend well to War Caster anyway, so you've got a good point there. Thanks!

Lol "only" 1/400.... bumping Con from +8 to +9 may drop you from a 5% chance of failure to a 0% failure on a DC 10 Con save, but having advantage on that +8 Con instead takes beating a DC 15 from 70% to 91%. Suffice to say, you can make percentages and math tell whatever story you want, but advantage on Concentration is always important for a character that will be getting hit by anything other than DC 10 Con saves, which at a certain tier are probably the exception rather than the rule.  

Warcaster feels much more fun at the table, providing several new "things you can do" rather than just a minor math bump. There's nothing like being able to cast Entangle or something (edit: Entangle targets an area not a creature... and there's literally NO other Action control or offensive spells on the Ranger's spell list that are Warcaster eligible, other than Steel Wind Strike picking only one target... nevermind, Rangers are uniquely bad for Warcaster!!!) for an OA instead of attacking, and really catching your DM with their pants down. It also means your DM is less likely to harass you about what you're holding in your hands when you go to cast a spell. But, Resilient (Con) is definitely doing some lifting on your sheet, giving you more HP, and increasing those Con saves by +1 from your extra Con modifier and +3 from your proficiency... that's pretty significant. 

Either are fine. You don't have any good Warcaster reaction spells chosen right now anyway, and you're a ranged character who doesn't hold two weapons or a weapon and shield.... so Resilient (Con) may well be the right choice for you after all. 

I'm forgetting that I'll be eligible for another Ability Score Increase in a few levels, too, so I could take War Caster then and by that point might have one or two spells that fit the requirements. Part of it is I just want to see what the fuss is all about with War Caster as it seems like a pretty exciting feat to work with, as you pointed out. Thanks, Chicken!

Rangers and paladins are designed to work in a way that does not benefit much from war caster.

I noticed above that Ranger's spell selection doesn't really suit it... but why wouldn't Paladins want to be able to make better OAs, and to keep up their buffs? Also, the S vs SM/SMV crowd seems to think that War Caster is a necessary feat tax for Paladins and Clerics that use shields anyway, though I don't share that interpretation...

Quote from Chicken_Champ >>

I noticed above that Ranger's spell selection doesn't really suit it... but why wouldn't Paladins want to be able to make better OAs, and to keep up their buffs? Also, the S vs SM/SMV crowd seems to think that War Caster is a necessary feat tax for Paladins and Clerics that use shields anyway, though I don't share that interpretation...

 There are very few spells a paladin can use as an op attack assuming you don't want to cast cure wounds(!) until you get banish at level 13 I think the only options are command and dispel magic the uses of the later being very niche.

If a paladin wants to use up a spell slot on an op attack their best option is usually smite and that doesn't need warcaster.

I wouldn't go as far as saying the war caster is a necessary feat tax for paladins and clerics. The most common spells that a S but no M spell on the paladin lists are cure wounds and lesser restoration, to heal a comrade the paladin can use lay on hands without dropping his sword and casting lesser restoration is rare enough that if it does mean any op attack canonly be a punch for one round it is a minor issue.  I have a cleric that pretty much never touches a weapon her offence is all spells I maxed her wisdom with her first to ASIs, at 12 I considered warcaster so she could cast spells with op attacks but she tries to stay at range sorarely draws op attacks so I went with resiliant even though it makes my con 17. At 16 and 19 I will take warcaster and aberant dragonmark (mostly for shield)  but not certain in which order.

Quote from DxJxC >>

Rangers and paladins are designed to work in a way that does not benefit much from war caster.

 To defend my answer, I am going to through each benefit of War Caster as it applies to Rangers and Paladins and compares to resilient.

You have advantage on Constitution saving throws that you make to maintain your concentration on a spell when you take damage.

So for this one, we are comparing to resilient (this is going to involve math and hypotheticals). Assuming you benefit from the +1 CON, resilient gives a +3 to +7 bonus to the save. Since you are a half martial character, you probably have around a +2 CON already.

So for a DC 10 save with +2 and advantage, you have a 87.75% chance to succeed. With a +6 (level 5), you have a 85% chance of success. Let's say at level 17 you take 40 damage from something, DC 20. With war caster, you have a 27.75% chance to maintain concentration. With resilient, you have a 50% chance of success.

So war caster is barely better at concentration at level 4-8, after level 9 resilient pulls away. Plus resilient applies to all CON saves, not just concentration and increases HP slightly.

You can perform the somatic components of spells even when you have weapons or a shield in one or both hands.

To benefit from this, you need to have combat spells that require S components, but not M components.

Paladins have 8 such spells, most notably cure wounds, heroism, and magic weapon-like spell's.

Rangers have about 10 (I didn't count any that only benefit archers as they will have a free hand).

And to indicate how generous I was being, I counted lesser restoration and protection from poison for both. Many of those spells were situational, and there were only 3-4 you are likely to have prepared much of the time.

In short, the go-to spells that these classes are known for don't benefit from this feature, and isn't worth a feat for the few that do.

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.

Final round. To benefit here you need a harmful combat spell with casting time of action.

I'll just list every paladin spell that fits: command, banishment, destructive wave. Yep, 3 and you don't even get the second until level 13, and the third at level 17.

Rangers have more, 5. They are all AOE/multi-targeting so you will have to waste most of the spell's potential to only hit 1 (assuming positioning even allows it) and the first spell is conjure barrage at level 9.

They really don't benefit from this feature.

I didn't take into account subclass spells, but I doubt that changes much.

To conclude, war caster is a great feat. Maybe one of the most beneficial ones. But it was designed for classes that spend most of their actions casting spells (namely cantrips) at enemies. Rangers and paladins were designed with spells that can already be cast while holding weapons and while using those weapons to take the attack action.

The concentration advantage is the greatest benefit for these classes and resilient is enough to match that while granting other benefits.

I just want to point out a fiddly bit with "magic weapon-like spells." They require V,S, and also require touching a specific object. I would argue that if GFB has a material component, then spells like magic weapon should, at a minimum, be ok to cast while already touching the weapon that you're required to touch (if not an errata to indicate that a weapon is actually required, like GFB got).

Just to point out for the specific character.

They started with 15 con and +2 on con saves.

Resilient con makes this 16 and adds proficiency. Proficiency at level 9 is +4.

So in this case, the comparison is advantage with +2 for warcaster or a straight +7 for resilient con. Resilient con is strictly better than advantage in this specific case. In addition, resilient con applies to all con saves and not just concentration. In addition, the +2 will never make a save against a DC of 23 even with advantage while the +7 will pass that on 16+ or about 25% of the time.

For this character, it is a no brainer - resilient con is far better than warcaster for making concentration saves ... the only reason to take warcaster in this case is if you want to cast a spell as an op attack or want to be able to cast spells with both hands holding something.

That was pretty thorough!

I think the advantage vs. higher bonus math can Be described more clearly... disclaimer, all math skipped in favor of just trusting https://statmodeling.stat.columbia.edu/2014/07/12/dnd-5e-advantage-disadvantage-probability/ 

Assume Warcaster is always rolling Advantage on +2 (con 15), while Resilient gave us +1 Con mod (con 16) and either +3, +4, +5, or +6 prof bonus (Tiers 1/2/3/4 of play).

DC 10: 88% Warcaster at all tiers, vs. 85/90/95/100% resilient.

DC 15: 64% Warcaster, vs. 60/65/70/75% resilient

DC 20: 28% Warcaster, vs. 35/40/45/50% resilient.

So... yeah, Resilient is SIMILAR to Warcaster in T1 and T2 (except at very hard con saves from massive damage), but strictly better in T3 and T4. But, resilients only other bonus is +1-20 HP, while Warcaster has the other benefits for OAs and Shield use...

I think most games, a player should know if they’re building for eventual T3+, or playing a low T1 & T2 game. For low level adventures, I think Warcaster is probably worth prioritizing, IF you have useful OA spells. For a Ranger and Paladin, looks like that might require MC or feats, though I haven’t closely reviewed all subclass expanded spell lists, that could change things...

This is an old thread, so sorry for necro-ing it but I stumbled upon it and wanted to also throw out that as a Paladin you also have your Aura of Protection that adds your Charisma modifier to all of your saving throws. So a good charisma of 16 or 18 for Paladin is a +3 or +4 as well to add on top.