Welcome aboard.
My son has an M&P40c and loves it. I have two fullsize M&P's, a 9 and a 40 and I love them both. I carried a S&W3913 for years and now carry the M&P9. That will probably change to the M&P40 after I get some more rounds thru it.
Nothing wrong with your model 59, but once you start shooting an M&P you will find the consistent trigger pull on every shot to be very nice.
I haven't had an oppportunity to shot my son's 40c, but I will next week when we get together in Yuma for dove season. Based on how I like the 40c I will make a decision on whether to get the 40c or the 9c.
Good luck on your decision.