It's my opinion that the only things you will gain in a .357 J-frame snubby are vicious recoil and longer recovery time for any follow-up shots that might be needed.
My favorite lightweight J-frame Centennials are .38 Specials. I shoot target wadcutters in them for practice, followed by a few +P stompers. I doubt that a bad guy hit with a +P .38 instead of a .357 would know the difference, and inasmuch as shot placement counts more than power, the .38s will be easier to control.
If you really have to have a snubby S&W revolver in .357, I would strongly suggest getting a K-frame Model 19 or a Model 66. They are heavier, controlling recoil better, and offer the advantage of a 6th shot. With the right holster, stocks and covering garment, they are not all that hard to carry discreetly.
John