The time of year you do this makes a big difference.
I have 100' of 5/16 grade 70 chain and have pulled over scrub oaks up to about 20' diameter at the base with no problems in early spring when the ground is wet enough to be soft, but dry enough to give good traction.
Later in the year, the ground is hard and the same size tree will just laugh at me.
That works fine for 1 or 2 trees. For a large number like you have, the excavator is the only way to go. Think about what you want to do with the wood. Out here, that would all be good firewood. If the trees were laid down, side by side, in several piles so it wasn't too dangerous to cut them up into 18" pieces they could be sold to people who would load them into pickups and drive them off. Gather the rest & burn it in piles. The ash will fertilize your food plot.