This likely won't be helpful, but here goes:
My biggest issue with the GAP round is ammo availability. Go online right now and compare prices of ACP vs GAP ammo (at the places you can find carrying it). $4/box more for 50 round boxes of GAP ammo. Multiply that times what you'll need for an entire department and it adds up hella fast. Now, I realize departments don't purchase ammo online, but rather through distributors, so I bring this up - remember just a few years ago when people couldn't get ammo after President Obama was elected? Ammo was in short supply for everyone, departments included. While distributors/manufacturers said replen was going to police and military first, that doesn't change the fact some departments were running short on training ammo. Very few people manufacture GAP ammo to begin with as the round is just not called for like with other cartridges. Also, the ammo your department has currently selected (brand, bullet weight/design, etc) may not be available in the GAP round. Of course, if you department does things right, you'll T&E all gun models and available duty ammo variants before making a final selection.
FWIW - Federal HST data shows zero (let me say again - ZERO) difference between .45 ACP and .45GAP. But, it boils down to actually finding a reliable and consistent source of ammo when you finally choose something.
Of every one hundred men, ten should not even be here. Eighty are nothing but targets. Nine are real fighters, and we are lucky to have them, for they make the battle. Ah, but the One... One of them is a Warrior... He will bring the others back.
"Wrong door, buddy!"
Let no man's ghost say my training failed him.