I'm surprised no one has asked what sort of Western adventures you want to run, which makes a very big difference in the sort of systems that should be recommended to you. What sort of games are you expecting to run?
Do you want combat to be gritty and realistic, or do you want deaths to be rare and violence to be stylized?
Do you want combat to be the focus of play, or do you want more cerebral drama based games?
If you want to run, "The West as it Was", you'd be better off with Aces & Eights. If you want to run classic John Wayne style Hollywood Westerns, you might be better off with Boot Hill 3e. And honestly if those are too lethal, you could run a more heroic western with something like Mutants & Mastermind set to you PL5 or such, and then have the capacity to switch to fantasy western, weird western, or whatever. And it might be interesting to strip out some of the setting of 'Dogs in the Vineyard' and run a game where the PC's were a Marshall and his deputies in some frontier boom town.
I don't know much about the system, but when this topic has come up in the past lots of people recommended 'Sidewinder Reloaded'.