Until I read your post I was going to suggest the .45-70. However since you're going to use it mostly for cowboy, I would say get the .45 Colt. BUT...I wouldn't use the .45 for deer or bear until you started hand loading for it. But why not start hand loading right away? You can buy cast bullets and brass in bulk quantities for cowboy shooting. Probably for just a bit more than you would for a few boxes of loaded ammo. And when you decide to use it for hunting you can buy a box or two of jacketed bullets if you want to and not worry about leading your bore with the increased velocity.