I like the .357 and own quite a few of them. But I consider full house magnum ammo to be more of a field load. Something you carry when out in the woods hunting or where some critters may bite.
On of my more frequently carried revolvers is a 3" S&W Model 13. Yes, its a .357. However, I normally load it up with .38+P ammo. The reasons are simple. Less recoil, better accuracy, faster follow up, much less fear of over penetration. Its just a much better load for typical urban carry.
So NO, you don't need a .357 Magnum for self defense. But I ain't gonna knock you if you carry one.