I own the full size m&p 40...love it like no other....never held a compact size m&p...just a G27 and i love the feel of it in my hands...never shot either however...
Smith, while I prefer my 1911 for protection (just that mystic .45 thing) I wouldnt think twice about my 642, That is the gun that truly goes with me EVERYWHERE. If I am ever not carrying I have my 642
I voted for the 642. Cheaper ammo to practice with, better trigger than the M&P and its not a glock!
Seriously though, if you're gonna have a carry gun, it's best to shoot it often and know it will go bang everytime. Can't beat a .38 +p revolver in that category. Yea, glocks are reliable, and it can carry more rounds, but I'm not a glock fan and everyone owns a glock. I like to be different! I'd love to have a .357 S&W or a smaller .38 spl for a bug to complement my Baby Eagle.
M&P .40 is what I carry and I love it. I like the 642 option as well, but it would only be when I needed a smaller or lighter gun. I personally like the 11 rounds of .40 for carry use.
I do carry a revolver too when it seems needed, but for daily carry it would be the M&P. If I was to get a glock it would be a 9mm and not a .40. That is my anyway.