I have the 9mm full size version. This gun comes with three backstraps that can be changed to fit the shooter's hand. I took this one to the range and use the smallest grip as I have small hands. After shooting it some, I sent it to Burwell's Gunsmithing and had a trigger job done. Now, I have something. This is a very reliable pistol and for the money, you can't beat it.
The M&P is my fun gun. I bet my life on the P229 everyday and could easily put the M&P in that category. The M&P is half the price of the Sig.
Go to a rental range and rent one to see what you think. Smith and Wesson is making huge money on this gun because police agencies are giving this gun to their officers and the scores are going up on average about 20% per person. To me, that's pretty impressive to be able to make a blanket statement like that. Several local police agencies in North Carolina have gone to the gun including NCDOC, Roanoke Rapids Police and many others and Raleigh PD is currently testing the gun.
Good luck to you.