I've owned and shot an M&P9 FS at and IDPA. In stock form with stock trigger it was pretty good even for a newer shooter like me. That says something about the M&P line! My roomate has both the G19 and G34 that he uses for IDPA as well. If you shoot the Glocks better due to the grip, then the G34 would probably serve you well.
Otherwise I'd stick with the M&P. I'm a big fan of M&P's and have owned both the 9mm and 40 full size.