I have a Glock 21 Gen 4 and a SIG P320 post-upgrade. Both are soft shooters and flawless performers, but I shoot the P320 better than the Glock, probably because the grip fits me. It's a fantastic shooter and very accurate.
I've shot the M&P45, and while it was relatively ergonomic I just didn't care for its shooting characteristics, especially the trigger.
I've heard good things about both the XD45 and the USP45, but have had no chance yet to try either one. My only other experience with full-size .45s is with metal-framed guns (P220, 1911) and needless to say I much prefer the metal framed 45's to polymer.
Biggest advantage of both the Glock and the XD are the standard capacity of 13+1 vs. 10+1 for most of the others.