As much as I like the .454, I'd lean toward the .44 magnum Marlin in a rifle. While the .454 has PLENTY of power (especially penetration), and you might be able to use .45Colt ammo in it (some will work, some won't), it's just not needed for deer size game. When fired from a rifle/carbine the .44 magnum gets a 400 fps velocity boost over a revolver. That's good enough to 150 yards. Also the Marlin is easily scoped. The cost of ammo is a lot less with the .44 mag as well.