As an old retired cop who carried J-frames on a regular basis since 1977, I prefer the 340 M&P or 640 (mine is a -1). For ammunition, I carry the Buffalo Bore 158 gr. +p LHP at a true 1000 fps out of the 2" barrel. I generally pocket carry the 340 M&P, which I prefer due to the Scandium frame due to durability over the straight aluminum frame.
For OWB/IWB carry, I like the 640-1, but generally carry the Buffalo Bore also. Both guns are easy to conceal and carry.
I was never a revolver fan but picked up a M&P 340. I've carried it almost daily for well over a year getting on 2. I have a total of 500+ 357 and 500+ 38 thru this platform. Difficult to shoot yes, but if you shoot a little frequently you can be pretty darn accurate.
I also carry the Buffalo Bore but LSWC 158gr. BB line of ammo meant for the snubby J's are truly fantastic.