Re: m&p compact
Both my wife and I carry M&P 40 compacts. I can't recommend one highly enough. My admittedly limited experience with the compact 9mm M&P has shown those to be as reliable and accurate as the .40s. When my wife picked hers up initially, it would lock the slide back with one round left in the magazine. I contacted S&W, they sent a label to us and had us box the gun up and ship it to them. Had it back less than two weeks later with a new slide release and haven't had another issue out of it. My compact .40 is just as accurate in my hands as a Sig P239 and has less recoil than one of those in .40.
One of my friends has a Springfield XD40 subcompact that he loves. I've shot it and it seems just fine to me as well. He hasn't had reliability issues that I know about, and people seem to use the XDs as much as M&Ps. I personally prefer the M&P - it just feels better, carries well, and looks better to me. I don't think you could go wrong with either of them, but if you're already familiar with the full size M&P I see no reason not to get a compact version.