Wow, way to stick with the OP's request of "info on these choices". Sorry about your experiences, but perhaps he has a great dealer? Mine is pretty good, they just built a new location where they keep about 200 tractors on the lot (all Mahindra except a few trade-ins), a ton of implements, and advertise their parts department as having a million dollars in inventory...
Welcome to TBN! First, the 5010 is made to be a big basic workhorse. The 35 series generally have more bells and whistles and are a little more compact in overall dimensions. The 3540 is the new version of what I have, and the 3550 is the slightly larger 50HP variant. A lot of what you are talking about doing, dragging logs, plowing, etc., is going to be better performed by a heavier machine (sorry Kubota fanboys). Sure you can add weight to a lighter machine to help it along, but you can add weight to a heavy machine too and still be able to build more tractive forces than the lighter machines.
Your choices are among the heaviest in their classes, so for the tasks you have laid out, in my opinion you're on the right path.