45hp is plenty of power for dragging firewood out for the homeowner. As you get above 45 hp. you get into larger frame tractors that are harder to get around with in the woods.
Also, the trailer or pull capacities are more suited for the amount of work that your going to want to do in an afternoon.
For instance, a 150hp. Ih 1566 can pull a semi trailer sized load of wood, but thats alot of wood and who wants to manuver a semi thru the woods.
You should stay way from fourwheelers for skidding logs and such, they are not designed to be a farm tractor or a log skidder. Alot of times their gears are too high, and they are not built heavy enough.
All this comes from experience running a firewood business off my fathers 400 acre farm / woodlot in potter co. This might not work for everyone, but this is what works for me.
Ericjeeper, try to always pull loads from the rear of the crawler. When you pull loads from the front, the slack in the track chain builds underneath the crawler rather than on top, that can cause a track to slip off and is very hard on the undercarriage.