Welcome Action,
I own a Big Boy in .44 mag and a friend of mine has a .357 in the same model. Personaly, I see very little diffence in accuracy. If you were to hunt with it you might be checking your ballistics. Being your using this rifle to plink you may want to consider the .44 only because you will have an option to shoot .44 mag. or .44 specials or even spacific cowboy rounds. Just something to think about. Which ever one you buy, you won't be sorry.