I'd choose the .45/70 for several reasons.
First of all, there are so many more options when it comes to factory ammo. Since the rifle you've chosen isn't a LA, you have an even larger selection of viable loadings as you needn't worry as much about OAL affecting feeding or using pointed bullets.
As a handloader and bullet caster the .45/70 would also offer you a much greater selection of components, both ready-made and DIY. More moulds in more styles and weights, more brand options for cases, etc. and many more choices for jacketed projectiles. The only caveat I see is that some, if not most, manufacturers' .45/70 chambers are somewhat short-throated. Only a critical factor when very long, heavy bullets and stout loads are contemplated but worth considering before you start experimenting with them.
While I may never get to fully exploit the extra versatility offered by the .45/70, I personally like having the options. I ain't dead yet, and I just might get that chance at a bison before I go.