Ive never shot a Glock.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.
Mags were a major issue. I got some a few months ago and havent checked supplies since then. Unfortunately it is or was an issue.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.