my dad got an M&P 9, very nice pistol, the adjustable backstraps really make sure it fits your hand. Its pretty accurate for an auto. Don't have a huge number of rounds through it yet but its been very reliable. the Smith and Wesson warranty is very nice and the rebate and extra mags is a nice bonus.
I have a glock, nice pistol and accurate but not anywhere near as comfortable in the hand. The triggers are very similar with the same type of safety. Take down of both is very close. the M&P does have a mag safety which the glock doesn't.
the M&P 9mm holds 17 rounds in a very small grip.
Loaded chamber indicator is nice on the M&P which the glock really doesn't have.