Can't tell you much about the .45, but I have the M&P9 and I like it a lot. I think they are well designed guns, but I just purchased a new XDM9 and I think I am going to like it more than the M&P. I would look hard at the XD45. I like the grip safety, striker position indicator and loaded chamber indicator.
It is probably just my method of holding and squeezing, but with the M&P, I tend to pull slightly to the right when the trigger breaks. Handguns are such personal items. What works for one person doesn't work for another. Good luck and good shooting.