Ammo seems to be the biggest issue with 22's.
All 22's I've owned do very well on Federal bulk bricks, but not so great on other brands of bulk.
I think a 22 would be fine for SD on a good quality ammo if its proven thru your particular pistol.
fwiw... the longer I carry, the more I get sick of it, the more I start thinking about smaller pistols. I too am starting to look seriously at mouse guns, including the NAA revolvers.