Alex T:
Obviously you are selecting from two excellent firearms, which makes it pretty hard to go wrong.
I am a great fan of the Ruger #1 and enjoy shooting mine very much. I keep mine scoped with a Leupold 4 power, and with our factory ammo it will routinely deliver MOA or better accuracy. It is elegant, compact, and utterly reliable in function. However, it does kick substantially harder than the Marlins in their various configurations. By comparison, the Marlins deliver about 1.5-MOA, which is quite good considering that the caliber is not a long range caliber. The Marlins are also quite strong, and will deliver power more than adequate for the largest game. Although the Rugers are stronger and will accomodate more potent loadings, the recoil generated by such loadings will equal or exceed the recoil levels of the 458 Winchester Magnum with factory loads. This is due to the light weight of the Ruger #1 when chambered in 45-70. When the Ruger #1 is chambered in 458, the gun carries about 2 pounds more weight, which tends to decrease the recoil effect. To the extent that speed of fire is a consideration, the lever-gun clearly has the advantage. Also, when hunting, the lever-gun allows the shooter to reload without having to take his eyes off the target, whereas the single-shot requires the shooter to look at the gun during the reloading process, and then reacquire the target. This delay is a significant shortcoming if a second shot is required.
Since you are selecting from two excellent firearms, you probably can't go too far wrong. However, if your interest is in hunting, I would think that the Marlin would have the edge. If your interest is just target shooting, then it is not such an easy call. It is true that the Ruger has greater inherent accuracy potential, but the Ruger also kicks harder, something that can easily cancel out the accuracy advantage.
Best regards, Randy Garrett
www.garrettcartridges.com