I could never get into Glocks... Boring plus the trigger sucks.
I really like the M&P line. Currently have three different ones and have owned 5 total. It kinda comes down to personal preference, tho.
I've had both, and liked them equally. To me they're pretty much the same gun.
My problem was finding M&P magazines - after ten months of waiting I gave up on S&W and went back to Glock.
Just my 2 cents.