XS Big Dots are certainly a good option but there is a bit of a learning curve/familiarization period. I would say they are an excellent defensive sight that you can pick up in a hurry and put holes in things within 10-15 yards.
My biggest beef with them is that windage is super fast to pick up, but elevation is a bit of a free for all since you are trying to line up the edges of the dot with the edges of the V-notch. I often wind up with centered groups that are spaced out vertically. Things inevitably tighten up after warming up.
Incidentally, after 4 months I am swapping out the pair of Big Dot's I have in my P320 I am swapping out for Trijicon HD's yellow's which are my go-to carry sight as soon as they arrive in the mail. Those are what I have in my carry G19 and they are awesome. That's my vote.