>>63832385
The 45 will have front serrations, slightly flared magwell, and a DLC finish.
The 19x will lack front serrations, has a pvd brown finish, has a weirdly constricting mag well because it has a lanyard plug thing (regular Gen 5s still have a hole if you really want to use a lanyard), maritime spring cups, and night sights.
IMO, Ameriglo night sights are nicer to use than the Glock OEM ones (which are Meprolight I *think*), and maritime spring cups are like ten bucks if you really want them. I’d lean 45 pretty comfortably, myself, unless you really like brown.