Originally Posted by
TOF
Purchasing a Pistol doesn't require a life long commitment to that particular pistol. As stated above, try a few and pick one without over analyzing it. If you determine in a few weeks or months it just isn't for you trade it for a different one. Better yet get a second and hang on to the first in case you change your mind again. The cost of trading among plastic fantastics is no more than the cost of 3 or 4 boxes of defensive ammo.
That said, my preference between .40 and .45 is .45. I have owned and fired thousands of rounds in both and find the .45 to be more comfortable to shoot in my arthritic hands. My in depth comparison was with M&P40 and M&P45. The M&P9 was lighter recoiling but not enough to sway me in its direction.
Enjoy whatever you choose.