The main job of the gun is to convince me that the Glock is worth owning and using for Carry and Range.
I think that the G19 is the sweet spot for what you need. The G17 is significantly larger and only nets 2 more rounds. I prefer the Gen 4 models because you can add various sized backstraps to adjust the grip. If it has to be a .45 I'd go with a G3oS.