Based on your question FQ I would go with the .454.
I am a .500 magnum guy. I have a six inch Performance Center with optics. It will drop a white tail at two hundred yards, and I have seen it used on Brown on the islands of Alaska (can't remember the show, but it was Tom Kelly from S&W). I have even talked to Tom Kelly about optics choices for mine. I want to use it on a black bear hunt some day provided I can do it in the States.
Down side of the .500 is that I can down load rounds, but I can't purchase lower power like using .45lc in a .454.