I prefer the .357 Sig recoil. It is different type of recoil to me. It feels more like a normal high powered round and not snappy like the 40.
My first M&P was a compact in .357 Sig and it came with a 40 barrel also. I bought a factory 9mm barrel for it to have all three calibers. I would carry with the .357 Sig barrel and plink with the 9mm.
Yeah I ran 9mm during a USPSA match it was easy running and easy to stay on target when you are used to the 40. Will be sure to post back when I get a chance to grab or reload some 357sig and hit the range.