I love my XD 45 Gap. Same performance is ACP, yet the firearm is smaller. Recoil is not bad either.
The ammo, it is less avail at local stores, however if you go online on Natchezss.com or the likes, you can find it in stock and for less. Natchezss has it for $22 a box, Try finding 45acp for anywhere near that right now.
Other option, is it is an excuse to reload. 45 GAP reloading is the same dies as 45 ACP. Only difference is the brass, obviously, and 45 GAP uses small pistol primers instead of the large ones in ACP. So once you have the brass, in theory to reload GAP would be c