The fellow I mentioned that owned one, used his behind his ATV with no problems, but his land was very flat. I wouldn't use it behind an ATV on hilly land, although perhaps they have surge brakes on the trailer?
Using it behind the tractor is probably a much better match with any sort of hills. Of course, it just depends on how much you load it up, and how heavy the trailer is to begin with. I venture a guess that the trailer alone is probably close to the max you should pull with an ATV on hilly land.
I think the reason more people don't own these, is due to the price. It is a very "job specific" tool and demands a high price, it's not very useful for anything other than hauling logs, so it's tough to justify for the homeowner or small business owner. It would really need to increase production quite a bit to make it pay for itself over time.
The cost is the only reason I don't already own one. I've often thought of building one, but they're not cheap to build either!
I think an excellent alternative is to buy, or build, a log trailer. Then purchase, if you don't have already, a FEL grapple for your tractor, load the trailer with the tractor and unload it the same way, or possibly incorporate a dump feature. It wouldn't be as "good" as a dedicated log trailer, but it's a whole lot more useful for many other things. What is 200 face cord equal to? I guess around 60 or so cord per year? If you could increase your production, or decrease the time it may take, and make it work from a cost benefit standpoint, it may be worth it???