I have the 1894fg in .41 mag (and a bisley blackhawk and 6" 657 companion pieces). It's an excellent level of power for this platform, I think. It did, however, take a good bit of shooting to settle down into an accurate shooter. In my gun, for instance, the bullet I would have wanted to use for economy, the Remington 210 jsp, would not shoot for beans. After a few hundred rounds (during which the barrel was presumably smoothed out), it did get to where I can shoot 2" or so groups (@100 yards) with Hornady XTP's.
My preferred load, though, is Lil' gun and a 250 gas-checked cast bullet, like Sharps Shooter--though I use a pinch more Lil' gun and a leadheads bullet. The high speeds of a carbine put the XTP out of its suggested velocity range. If you want to use a JHP, the Gold Dot would probably have the best chance of performing well and holding together on impact. A Marlin probably won't feed the longer OAL of the 255 or heavier cast bullets; I know mine won't. It will hold about 3" with my 250 cast load out to the functional range of the gun, about a hundred yards. To me, this makes it an ideal brush gun for deer or any medium-sized game. I wouldn't hesitate to shoot a big hog or black bear with it.
I suggest a Williams aperature sight for the receiver, and perhaps a hi-viz fiber optic bead to replace the stock front. This combo, on my gun, is very fast and as accurate as the gun is able to shoot. Oh, and a Wild West trigger makes an amazing difference.
If you want a gun that does what the .41 can do, and you're prepared to reload for it and work with it, it's a neat gun. If you want something easy to shoot out of the box with most any factory ammo from any mom & pop, the .357 (which I also have) is a great gun within its limitations.
