Go out an buy it. They are GREAT guns and VERY strong

My Family, Associates and Students have put tens of thousands of rounds down range with ours so far.
I even have a compact for pocket carry.

AS you have already noted with the folks that you have talked to there is no definitive information on why they do not like it, just lots or Rumor, innuendo and Hearsay

After you have put a few hundred rounds through yours, you can make the decision yourself.

I am a HUGE fan of the 357SIG cartridge. I was first introduced to it by Texas DPS when I was working in Dallas County back around 1993. Lots of caps have been busted since that day

I have many S&Ws, SIGs, HKs and other pistols chambered for this fine round but the Smith and weson M&P is the only plastic framed, striker fired firearms chambered for the 357SIG that I own.