We have a 125 acre farm that includes wooded terrain that's been logged. I went the 40hp route with a MF 1643 Hydro. It was an ok tractor, but I kind hated it because the hydro was a weak whiny b*tch and I was constantly finding the tractor was not quite up to the tasks I needed to do.
Ended up going to the 4707 and now I don't worry about having enough tractor. Bonus points for the cab and just how comfortable it is to operate. The radial tires provide a smoother ride, the cab is rubber mounted, the floor has a rubber mat, and the seat is air ride. I also got the upgraded FL series loader with self-leveling.
If I need more, I just use my JD 410.
My suggestion is to get the bigger tractor because if you don't, you're just delaying the inevitable.