M&P!!!
The M&P has metal sights, the Glock's are plastic.
The M&P has a through-hardened stainless steel slide, the Glock has a case-hardened coated steel slide.
The M&P has a stainless steel barrel with a fully-supported chamber, the Glock has a blued steel barrel with a partially unsupported chamber.
The M&P has an ambidextrous slide
release, the Glock has a right-handed slide
stop.
The M&P has a more ergonomic grip with interchangeable palm swells, the Glock has a flat grip with a one-size-fits-all mentality.
The M&P has standard metal drop-free mags, polymer-coated Glock mags often have to be pulled from the well when empty.
The M&P has replaceable slide rails, to replace the slide rails on a Glock, one has to replace the entire frame.
All M&Ps have accessory rails, some compact Glocks lack the rail.
The M&P has a larger trigger guard to accomodate shooters wearing gloves, the Glock is more difficult to shoot wearing gloves.
S&W's customer service is second-to-none, Glock's is reported by many to be questionable.
The M&P is Made in the U.S.A., the Glock is made in Austria.
Despite all the advantages the M&P has over the Glock, it costs, on average, about $100
less than the Glock.
If you are asking this question because you are considering purchasing one or the other, you should read this before making your decision.
http://www.thegunzone.com/glock/gindex2.html
Well, that about sums it up. I was going to buy my second Glock this past spring, but then I looked into the M&P. I bought the M&P instead. I just purchased my second M&P, and my Glock is for sale.