I've 2 Yamahas. 1 a 350 Big Bear 350 with full time 4X4 and the other a Kodiak 400 also a full time 4X4.
Essentially the same except for 2 notable things, the engine and tranny. The engine diff is obvious, but the trannies arn't. The Kodiak has a Hi - Low option.
Now, I married a gal with a small ranch in Nebraska, and I put in feed plots for deer, turkey, quail and phesants, at first I attempted to use the 350 BB to work the ground (it hadn't been tilled for years) and had great difficulty. The wife suggested we try the Kodiak in low
The diff was obvious, in hi it pulled much better, in low it was awesome.
Our neighbour down the road tried out his 500 2 wd Suzuki and it didn't cut the mustard (ground
)
It's your choice, but if your'e going to plow, and work dirt the 4X4 with a hi/low gearbox is the ticket. The additional cost will be worth it in the dirt, on the trail and at trade in time.