Not sure about the M&p45, but my buddies 40 is awesome.
For the money, I personally think the M&P and Glocks are the best. So either is a great choice.
I own a G30, Glocks are great guns. Shoots accurate, easy to clean, will last almost forever.
But... It's a fatboy. like real friggan thick. you might as well get the full or slim, because the guns so thick it almost makes no sense as a Sub. If I could go back and do it all again, I would have bought either a G36 Slim for carry, or G21 for non.
With that said though, I love my G30 and will keep it forever.
Anyway, check this thread out for the G30: