The most I've ever put through any of my Glocks at one range session was 200 rds. I don't know what it is, but with the stock trigger, I just don't seem to be as accurate. Between my 4 Glocks (27, 36, 30 and 19), I've put probably 10k rounds through them. Once I get the springs and connectors replaced, they work fine.
My M&P is new and I've only got 250 rds through it, but the trigger out of the box just seemed to work better for me.
Maybe it's a mental thing with the Glocks? Like I know I've had trouble in the past so now I just expect it? I do agree that going between platforms isn't probably the best idea, but no matter what, I can't get rid of my Glocks because I like them. I bought the M&P just to try something new and really have enjoyed it so far.
What you need is a nice shiney, brand new Ruger SR40S and let ole mdog get one of them 45's out of your way. You'll feel better in no time.