Having owned, and compared, the M&P45, Glock 21, HK45, USP 45 and a variety of 1911's...
The most pleasant to use is a full sized, all steel, 1911.
It has the best trigger...short, light...but the 1911 platform requires attention to ensure reliable cycling....if you want 'stone axe reliability' with all loads, 1911's are not your cup of tea!
I found the M&P45, and the H&K Tactical and Compacts too 'snappy', even with generic 'ball' loads, never mind 'warm' personal defence loads.
Of the 'plastic' 45's, it's a toss up between the Glock and the USP.
(In the HK45 vs USP45 battle, if I'm going to put up with a crappy DA pull, I would also want an external safety...again...personal preference.)
Personal preference has a huge role to play in what works for any individual.
My overall favorite, based on comfort, grip preference, accuracy and reliability.....
The G21....least expensive, most manageable recoil..just plain works! The trigger, which is consistent from pull to pull, is easy to modify...pick the desired weight, and it's possible to mix and match inexpensive, and easily obtained, parts. Reliable....it doesn't get any better than Glock!. The only issue is the magazines...I believe the newer SF versions are 10 rounds...not 9.5 like the G21!
I have handled, and prefer the grip on the newer G21SF, but there's not enough difference for me to change from my G21. Besides, I have a 10MM KKM barrel which just drops in....change the barrel, use some G20 mags, and now I have two guns in one...what's not to like!
(Personally, while at first I liked the smaller, more 'ergo' grips on the HK45 and the P30L, after shooting them a fair bit, I found them to be too small for my average sized hands....I found it difficult to position my hand so that my trigger finger wasn't going too far into the guard, leaving my first knuckle, not the pad of my finger, on the trigger)
YRMV.....