I really don't think there is a big difference in drivetrain, Same diffs. The J5 just seems more suited to logging. Easier to addapt to your needs!! The older sw's did come with cabs, nice in winter, and wider models which would make hauling easier. The newer SW's, have modern comforts, heaters, but are really for sidewalks!!! Between the two I would go for a J5.
If I was real serious about logging for years, I would get a muskeg!!!!!!!! Its a tank!!! Can't throw a track, good up to a few few feet of snow. Last muskeg I had had a 20k winch in the dump body!!! Would have been great for logging. The older muskegs like Pixies are awesome for logging!!! Heat in the winter!! Minnesota Outdoors has a few. Take a look and think logging!!!!
You sure are right about having to pack your trails for pulling loads!!!