I have never owned a M&P in .357 SIG but if you check out the website WEAPONSMAN.com they had an entry on March 30,2015 about all the problems with the .357 SIG model.
North Carolina Highway Patrol dumped them in 2013 because of numerous issues and Texas DPS dumped them in early 2014.There is also an article about the .357 M&P in Truth about Guns entry -April 11,2014.
This is all second hand info but to me it seems like a lot of incidents to discount Internet rumors. Good luck....
He is right about the N.C. Highway Patrol. They went back to Sig for this platform. My brother is a Trooper and he said that the Sig rep promised that they would switch back once they had the Smith version for a while. They did have some serious issues with the Smith but he said that he actually shoots it better than the Sig.
