I have a full size M&P in 357 sig. I personally think it's a good choice for personal defense. I've put mine through several different barriers including car doors, walls, cinderblocks, etc...all with outstanding results. as far as penetration goes, the 357 has outdone the .40, .45, or 9mm in my own tests. long story short, The 357 sig will destroy whatever, or whoever stands in it's way. I first bought the 357 sig compact, but it had some extreme recoil so I traded it back for the full size which was the same price. Nothing against the other calibers, for they will all get the job done, but the 357 sig is my carry weapon at all times.