Tough one. You could also wait for Sig to drop their P320 in 10mm later this year, and do a 3 way comparo between the Sig, M&P and your Springfield. Be cautious on letting that FS Springer go, though. It would not be easily replaced.
Dump both and get an EAA Witness by Tanfoglio. It's the most comfortable 10mm I've ever shot (and I've shot most) and is a tack driver. The Defiant 10mm is the same gun, same manufacturer, different milling and a different importer.
Which model(s) of Witness do you recommend? I had the least expensive full sized polymer model in 10mm at the time a few years ago, and it was less than reliable.
I have a XDM 10mm. It's almost NIB. Nothing wrong with, I like it, but Sprg. has discontinued it. Do I:
1. Keep it, or
2. Sell it now, and get the M&P10mm?
Are you aware of all the M&P 10mm problems that seem to be popping up?