</font><font color="blue" class="small">( I want to put fences up )</font>
What kind of fences? If you are planning on posts in the ground, you probably will want a post hole digger, and do not need a large machine to operate that. Other tasks using the tractor might be clearing the fenceline with brush hog/scraper/sprayer.
</font><font color="blue" class="small">( trails through the woodland )</font>
For this, something smaller, like a B series Kubota, may offer advantages due to increased maneuverability between and around the trees, although when you say 60 acres of woodland, that does seem to call for larger. How big are the trees? Are you planning to remove large tree?
</font><font color="blue" class="small">( mow the 20ac )</font>
I mow about 12 acres easily with a Kubota
B7800 and 60" brush hog. It takes about 1 hour per acre because some of the area is steep and rough, and the vegetation is dense.
</font><font color="blue" class="small">( and a trailer )</font>
Is the trailer to carry the tractor or to be pulled by the tractor? If you are going to be moving the tractor on a trailer, consider how much weight your current tow vehicle can handle. The ultimate deciding factor for me picking a
B7800 rather than an L series was to avoid having to buy a larger truck to pull it on the rare occassions the tractor might take a road trip.