@Talismina not bad but you're missing a few things in there- namely that the DC of 10 is the minimum, and also, a bit of context on what the effect is of your overall bonuses.
I didn't miss that, actually. I wasn't talking about the DC, but rather, what you need to roll to hit the DC. If I have 3 pieces of gear that provide +1 to saving throws, Bless is active, and a 14 con, I'm looking at +6 to +9 to my saves. So with a bless roll of 1, I'm looking at only needing to roll a 4. So DC 10, but only a 4 needed. Basically putting an advantage column next to a +resilient (and one more point from con) column for ease of comparison.
Of course, I am simplifying things quite a bit. Like the assumption that the +1 from Resilient will be combined with investing 1 more starting point in con, rather than the reverse of spending one fewer. And that, before you cap out the prof bonus at 4, Resilient will be weaker, but Warcaster will do what it does regardless of level.
Overall, though, I think if you're just looking for some help about concentration, they're about equal, in time, anyway. Warcaster is overall better at protecting your concentration, but it provides weaker benefits outside of that. But if you are serious about protecting your concentration, then you are looking at a situation where you are trying to avoid that 5% failure rate, are building more save boosts into your team, and so on, and yeah, then Warcaster comes out ahead. Which it should. It is the more specialized feat, after all.
I personally wouldn't recommend taking both either. Feats are too rare, especially with MC'ing in the mix. So just too much opportunity cost. You're better off getting the perks in other ways, like by making your initial class a fighter, barb, or sorc, or using a piece of equipment that gives con save advantage. Or just cheesing it with a camp NPC, if you want to go that route.
