Man, some of you guys probably suck at shooting M&P's...
I've owned a Glock19, M&P9, and XD40sc. I shoot the best with the M&P. No bias there, because that's just what I shoot the best with. The XD is a great pistol, and has a trigger much like the Glock's scissor-type safety but it has a short take-up before the trigger breaks. The Glock does not have the take-up and just breaks as you pull the trigger.
Nothing wrong with the M&P IMO, mostly just shooter preference and subjective experience. I shot my first IDPA pistol match with the M&P and was shooting bullseyes on the targets on the very first stage (and this was when I was a noob).
Each of them have a different balance, thickness, grip, and bore axis. Glock and M&P have a lower bore axis which makes them feel more natural. The XD has a thicker slide which kinda feels more front-heavy.
You can't go wrong with the M&P or XD, just go with which one you prefer. Dry fire both of them at the store and see which you like better.
Some people hate on the M&P trigger, I hate on the Glock trigger--and the Glock is my current EDC
