I prefer the M&P also, in both .40 S&W and 9mm. Another thing to consider, if you end up shooting a lot, you'll probably end up reloading. No problem shooting lead out of an M&P stock barrel. With the Glock, its up in the air whether you need a aftermarket barrel or not to safely shoot lead.
The hard thing about both pistols is that it normally takes a while to get proficient with either pistol. One gun may feel more comfortable in the shop, but that doesn't necessarily carry over to the range. The stock trigger pull leaves a lot to be desired, hence the very common initial problems with "low, left". Both are extremely reliable, but for me and my wife, the M&Ps are what we started with and prefer. And lastly, I'm glad someone finally said it, the M&Ps are just a whole lot nicer looking.