For me, smaller is better. I had a big Polaris that you could barely fit in the back of a pickup. I don't like pulling trailers, like to carry my flip over and scooter in the pickup so when I get home I just run in the garage and that's that. I think the Honda Rancher size is perfect (I actually have a Yamaha Kodiak which is the same size). You can run the thing up the ramp into your pickup with no drama. Scoot it around by hand and have plenty of room for your auger, buckets and other gear. Then I carry my one man flip over (I think it's a clam X, a pretty good sized one-man) on a hitch hauler. I don't have to take the hitch hauler off to load and unload the scooter with a tri-fold ramp. The disadvantage to smaller machines is their capabilities in deep snow and slush. You can help that quite a bit by chaining up with good chains. I use heavy duty light truck chains cut down to the wheeler size. Obviously, a big ATV with big tires and a ton of power will blast through snow much better and carry large loads better too.
For a one man fishing operation, I think it's the only way to fly. No trailer, plenty of room, can pull right into the garage without unloading. No fear when loading the thing into the back of the pickup. Real big ATVs can be sk=etch as heck loading into the pickup.