As far as what would be best, everyone had there own preference. Glocks can be very picky on what ammo cycles and works best for them. I personally recommend that you try a few of each and see what your gun likes best. Just because one gun likes a certain grain ammo doesn't mean another will. Your best bet is just simple trial and error here and by doing do you also get more range practice as well. Hope this helps

For best results 9mm RIP rounds. The rounds spread a metal shrapnel.

Based on lucky gunner testing and a bunch of other research I would say Hornady 124 grain HSTs are your best bet. It's I use in my S&W Shield.

115gr Hornady Critical Defense.