There's a pretty big difference between the two. The .348 is a couple hundred feet per second faster at the same bullet weight, and the sectional densities are much higher with the .348. While both have somewhat limited bullet options, the .348 has the 250gr Weldcore which is excellent on everything in NA, and for which there is no equivalent in the .444.
I have nothing against the .444 (and enjoy shooting them) but it's just not as capable. The Marlins are also not as nice a guns as the Browning M71s and even original Winchesters. The .444 does generally recoil less if that's a concern though.
