I dont have one go to saw yet. I usually use several, different sizes. If I really really had to choose just one, it would be in the 60 cc range, seems the best over all compromise for the wood I cut now. Anything that could run a 16 to a 24 inch bar and not be ridiculous. Talking stock saws with at most a MM and realistic tune.
If I skipped all large trees, and went back to just cutting small standing dead and blow down branches and thinning saplings, like I used to for my firewood with my little 30 cc saws, I could get by easily with my battery saw @ one charge per day, cutting like one inch to twelve inch size wood. I can get a lot of cubic feet of wood in the stacks by cutting a little smaller than most guys would cut. Did it for years, learned that cutting with a 30 inch bowsaw. Added bonus doing it that way, much less splitting and hernia sized big rounds to deal with.
So, chainsawing being loads easier than bowsawing, I would have zero problems doing 4 to 5 cord a year with the oregon saw, not even cutting every day, only cutting a couple days a week. That saw, my fiskars hatchet and fiskars supersplitter, plus a wheelbarow or the garden wagon, could do it all handily. I figured, after a lot of use, learning to use that particular saw correctly (a few test cuts will not give anyone even close to a realistic experience on how to use that saw correctly, it is just different from even a small gas saw), and measurijng what I got, if I really did cut every day, just one battery charge, I could get close to 15 cord a year.