Well, it's slightly confusing - the .357 refers to the size of the bullet. A 357 basically shoots .38 rounds; .38 is the size of the casing. There are three basic types of .38 rounds; the original .38 round, which is no longer in common use; .38 special, which has additional gunpowder, and is the traditional law enforcement round; and the 357, which has even more gunpowder. A box of .38 special ammo will cost ~$0.20 per bullet at retail pricing; a box of .357 will run ~$0.40 per bullet. (I've never bought plain .38 ammo.)

A .22 is a smaller bullet, and significantly cheaper; a .22 bullet will cost ~$0.02, which, as you can imagine, makes them a whole lot cheaper.

A .357 round packs enough punch that even a hyped-up drug user will go down, and doesn't have the painful recoil of a .44, so it is the preferred revolver round for self defense. Because of the expense of shooting it, however, it makes a very poor practice weapon.

It's -not- a hunting round, however, and while sufficient to such purposes, if you're looking for a weapon to take out anything larger than a medium-sized deer, you should go with something with more power. (And you really shouldn't get a handgun for hunting anyways, unless you're a marksman, as the reduced accuracy makes it cruel.)