If your rile is the Browning Traditional Hunter Single-Shot, I'd keep it. It's bound to increase in value simply because the chambering is unsual.
If it is the Rossi "Puma" copy of the Winchester M1892 lever action design, I dunno. that is too new to evaluate yet.
Speaking strictly of calibers, that .454 can shoot full-charge magnums, or the .45 Colt for milder recoil and target impact effect.
The .45-70 is one of the easiest cartridges to load for and versitile to boot. A classic brush buster and old-West aura too!
As for the Marlin 1895 series .45-70 rifles, I LOVE them. Great shooters, balance, and plenty of old west looks and feel. If you plan to shoot lead bullets, or you handload for that .45-70, I'd certainly get the ones with Ballard-style cut rifling, not the Micro-Groove barrels.
You takes your choice and enjoy.