I would take 5 rounds of .357 out of a good revolver over 7 rounds of .380 any day. I don't carry spare ammo...unless I'm carrying a revolver, then I carry a speed strip, because it's just so easy I don't see why I wouldn't.
Based on everything I have read I don't have much confidence in .380 for defense, nor do I have a lot of confidence in the general reliability an durability of the small .380 autos. To me, .380 is a "deep cover", carry when you can't carry a "real gun", or backup, type of pistol.
But a good reliable revolver, that I've put through its paces...I have confidence that thing is going to work. And I have absolutely no hesitation trusting the terminal performance of .357 magnum. Or even a good 158gr LSWCHP +P, or the Speer 135gr +P Gold Dot.
That said I'd rather take a Glock 26. I couldn't pocket carry either of the OP firearms, not effectively, so once we're talking holstered on the belt, I think a G26 conceals just as easily, really, and 11 rounds (minimum) of 9x19 in such a 'shootable' reliable durable package...that's really my answer.