I haven't made it a secret that I am a big fan of the M&P pistols. So between these two, I'd choose the Smith for myself.
However, if I were in the market for a larger caliber handgun (and I expect I will be before long) I would go with a 1911 .45
EDIT: @ 45acprules..... Glad you like your M&P. If you don't mind me asking....what agency do you work for?