G19 is probably a slightly better gun for CCW just because size. I like the M&P better though, overall, because it seems to be an up to date "current" version of the Glock, as Glock has not changed anything in a long time.
Here are some things to think about
M&P:
1.) Stainless steel
2.) Lifetime warranty
3.) 17+1 is nice
4.) Mag safety is nice for me (but you can get them without it), so is loaded chamber indicator
5.) Possibly cheaper than Glock, at least it is in Columbus, OH.
6.) Adjustable grips
7.) Truly out of the box ambidextrous
8.) Made in USA (factor for me, but others hate it or don't care)
9.) Takedown for me is easier than Glock due to Sig-like takedown lever.
10.) Steel Novak sights vs. Glock plastic sights
11.) Can shoot lead and reloads easily.
12.) Rockwell hardness = 68
Glock:
1.) Parts are avail. anywhere
2.) Not many parts in gun, so not much can go wrong (at least that is the theory)
3.) 1 year warranty (I think), although I hear they stand behind stuff longer than that.
4.) Durable tennifer finish.
5.) Torture test proven
6.) Holsters, clips, and everything is more readily avail.
7.) Mags for Glock are cheaper than M&P mags
8.) Their barreling is supposed to be more accurate, but can't shoot lead.
9.) Adaptability to shoot .22 and other calibers can be done on same platform.
10.) Rockwell hardness = 64
Maybe someone else can comment on kaboom factor of unsupported chamber versus supported chamber. I don't know much about that and am unsure whether M&P has a fully supported chamber or not. I believe they do.
Trigger is about the same to me and, honestly, if this is going to be your primary gun, you will get used to about anything as long as it is not total crap! Best to try it before you buy it. Go rent both!