The 790 and 990 are pretty old designs. Both great tractors...simple, reliable and easy to maintain. However, as they are both "Advantage" (i.e. cheap, considering their power), you get lower capacities in some ways..hydraulics, for example.
However, when you consider the weight of the implements you, as a residential non-agricultural user, will use; I think you'd find the capacities of the 790 quite adequate. The heaviest implement you will probably purchase would be a rotary cutter. A 60" cutter weighs 600-650 pounds, well under the capacity of the 790's 3 Point Hitch.
As far as dragging trees, the 790 can handle up to an 8" tree with little problem (you'll need MFWD and probably the differential lock now and then). The 790, although quite capable, is rather light (about 2200 pounds less ballast).
The 990 is obviously quite a bit more capable. You'd be able to drag larger trees and use a 72" cutter (maybe even an 84" unit).
All that said...I'd look at a 3320 Deere with the power reverser transmission. That tractor may fit your needs better...especially if you want a backhoe.
"Or should I not concern myself too much with lift capacity, because dragging trees is a job best suited for the FEL?"
You'll want to skid trees from your drawbar (steel bar with holes in it located below the rear differential). For towing, that's the strongest part of the tractor. I have used the FEL on occasion to move trees. These were lighter trunks and the only reason I did this was to prevent digging up the finished lawn I had to cross.
BTW, three things not brought up (or I missed them if they were):
1) Tire selection: if you're not going to mow a lawn with your tractor, Ag type (R-1's) would probably be your best choice for maximum traction. Make sure getting them filled is part of the deal.
2) Stall cleaning: If you're going to use your machine to clean stalls, you'll want to get a small enough machine to do that work. This, of course, would depend on the design of the barn and stalls. With 7 acres, I'd guess you're planning on having two or three horses. In that case, a suggested barn design would be the type with the stalls open directly to the corral or pasture (rather then the traditional design with the stalls off a central passageway through the barn).
3) Resale value: The Deere's will remain quite high (compared to a brand such as Farmtrac). That may not mean a thing to you, but is something to consider.
As many others have written, make this choice carefully. If you buy the wrong machine (size or power), you'll take a substantial depreciation if you try selling or trading the first two or three years (as you'd be competing against new tractors and better financing for new machines).
Good luck!