I bought my first M&P, a 40c after doing several weeks of research into its design, test firing one on the range and reading reviews about good and bad views on the firearm. After all that I bought it because the M&P design is a very simple, and reliable mechanical system and the feeding and extraction design has very little play. It is just a very well designed firearm. Assuming you do not try to put questionable rounds in it, or don't maintain it properly, it is certainly built to last.
I bought a Shield 40 just because of all the negative reviews it had when it first came out, cause I knew it wasn't the design of the firearm after all the research I have already done on it and I proved to myself those reviews were wrong and my Shield 40 has been my CCW since and the only issue I had with the shield was getting use to the thinner grip.