I voted 22 kit for Glock 19, because that's what I have (Advantage Arms).
Before I had a permit to carry, I had all kinds of potential carry guns, but once I started carrying daily, I realized I didn't have time to train with more than one type of gun, so I standardized on Glocks (I already had 2 of those) and I carry either a G42, G26 or G19, all of which work the same way with the same trigger - they're just different sizes for different clothing situations. I think it's actually an advantage that the 22 kit for the G19 is only about 95% reliable because every time a 22 round fails to fire, I get to practice a tap-rack-bang drill, which never happens with the center-fire rounds because they all fire and eject properly, every time. And it actually took time for the tap-rack-bang to become automatic. The first few times, I just stared at the gun for about a second when it didn't shoot. Unacceptable!
I also have a Buckmark but that's a target gun and I shoot it differently than my carry guns. For the Glock 42, 26 and 19 (and the 22 kit), I don't try to shoot small groups - I don't even measure my groups - all I try to do is to eliminate flyers and put all my shots on an 8-1/2" by 11" sheet of paper, at either 21 feet or 30 feet. For the Buckmark and other target guns, I try to shoot as small a group as I can at 15 yards. They are actually completely different tools for different purposes: one group is for SD, the other is for fun.
BTW, you can get extra Advantage Arms 22 mags from the manufacturer and they aren't super-expensive. I believe I have also seen them on either Midway or Brownell's (or both).