I've owned several .45ACP handguns. One of the best was a HK Mark 23; but, it is huge. Had several 1911's, hard to beat that platform. Recently picked up a STI Edge, haven't fired it much; but, it looks promising. The biggest surprise was a Shield 45. Unbelievably accurate, easy to handle and conceal and a soft shooter. Next on my list is a CZ97; my buddy has one. Great pistol.
I have yet to shoot a Glock. Folks swear by them. But, they just don't have the visual appeal to me.
Neither the M&P .45, nor the Glock 21 seem to offer much, IMO. But, I'll bet either, or both, offer more performance than I'm capable of extracting. I suspect a lot of the comparisons we read are subjective, based on the individual's likes/dislikes. IMO that is good, beats marketing spiel.