To expand on Halycon Styxland’s answer, let’s assume you have +2 from your Con, not an unreasonable assumption imho. Concentration checks have a DC of 1/2 the damage taken, or 10, whichever is higher. Focusing on the 10 since it’s guaranteed and many hits will be for 20 or less damage, you need an 8 thanks to your Con bonus.
Getting proficiency and thus an extra 2-4 means you need to hit a 6 at low levels or 4 at high levels and thus your chance of failure is 25% down to 15%. Not bad.
Getting advantage on the other turn makes it so your chance of getting a 7 or lower is 12.25%, straight away from level 4. That’s better.
In terms of stacking bonuses too the advantage stacks better- if you get a +3 from a Paladin aura or bless or something, without advantage you cap at 95% chance to succeed. With it you’d be at 96%, and you can get all the way to a 99.75% success rate.
However it should be noted, *both* of these effects can be obtained from items, and advantage doesn’t stack. If you’re wearing the moon devotion robe, Warcaster doesn’t do much for you and Resilient would be better. If you’re wearing the robe of supreme defenses, Warcaster is the far better option.
So of course The right feat depends as usual on what the context might be, but on a blank slate and in isolation Warcaster offers far more of a benefit, and has more favorable interactions with further save bonuses you might obtain.
Last edited by GiantOctopodes; 13/10/23 12:36 PM.
