To more directly address the question... I own an M&P9 FS and an M&P9c, and here's my experience.
The compact had 2 FTEs when it was brand new, but my DSW was firing it at the time, so it's possible that it was limp-wristing as she is not very experienced. It has never malfunctioned when I've fired it.
The FS had to be returned to S&W because some of my mags started refusing to drop free; S&W replaced the mag catch and the pistol has worked flawlessly since. I had probably done several hundred dry-fire tap-rack-bang drills before it had problems, so the mag catch had probably been through more torture than most of them.
OTOH after several thousand rounds, the pistol has never had a firing or cycling-related malfunction that could be attributed to the gun itself; the only times it has failed to go BANG were due to 2 handloads with improperly seated primers.
IMHO the main aspects where the Glock clearly beats the M&P are mag availability and prices, aftermarket support (but the M&P is rapidly catching up), and trigger reset. IMHO the M&P wins on grip feel, overall trigger feel (no "dingus"), factory options (you can have thumb safeties if that's the way you roll), factory sights, ease of disassembly, and let's face it, styling- after all, the Glock is the Volvo 240 of handguns in this regard.
I consider reliability to be a wash, other than the early-production M&P and early G4 Glock teething problems. S&W customer service is excellent; I have not dealt with Glock CS, so I can't honestly declare a clear winner here.