I think Rockstar chose outfits that fit John and Arthur well
I think the Gunslinger outfit for Arthur is good, but I prefer to have no neckerchief and an open collar personally. I also think the Summer Gunslinger looks good on Arthur, with an open collar and rolled sleeves. And I like John's Cowboy outfit too, I just wish they wouldn't reuse Arthur's model and just give it black hair and scars. If they just put a little more effort into John, it'd be vastly appreciated. So, because of John's rushed appearance, I'm going to have to say I like Arthur Morgan's Gunslinger outfit better.