I also have a few four wheelers, not as much acreage, but lots of deer (axis & whitetail) and hogs. As long as you clean the guns after each day of wheeling (I use brake cleaner first, and then a light coating of oil), and you should not have any reliability problems. The Marlin and SKS are extremely reliable guns, even if you don't dust them off every day.
If I had an extra couple of hundred bucks, I'd take the Marlin, buy a Weaver two piece or one piece set of mounts, some Weaver rings (available at most Wal-Marts), and then locate either an old El Paso made Weaver 2x or 3x scope (my favorite is a post with a horizontal reticle) (failing that, you can get a good 4x Nikon 22 scope for about $100) and you have in my view a perfect four wheeler companion, which I attach to the front rack or handlebars with U-shaped rubber clamps.
I put either a piece of bicycle inner tube over the scope to keep out the dust, or a specially constructed rubber scope cover which is a couple of bucks extra, and easily comes off the scope but either option keeps the lenses nice and clean.
I like the lower powered scopes because my eyes are older and help me locate the game more quickly than with open sights and allow a more precise shot when needed. I also have a ghost ring 336, and that allows at least for me a better sight picture than with the SKS.
I have been able to take lots of deer and hogs with this 336 scoped method. You may able to do the same.
That said, I also always carry a S&W 629 in an El Paso Saddlery shoulder holster for those very few chances when I have had a chance to sneak up on game (despite the four wheeler noise) on a hog or deer since we have very thick brush on our property.
On a few occasions, I have alse taken along an SKS with 154 gr soft points because of the 10-shot capacity and easier reloading with a stripper clip, but have yet to take either a hog or a deer with the SKS - the chance of a shot just hasn't happened yet.
Good luck with whatever method you choose, and you should not need to buy a new rifle to accomplish your goals.