Newton's 3rd law says that for every action there is an equal and opposite reaction, so when your two wheel tractor is wacking seven kinds of brickdust out of the ground it's doing the same to you. Some people love them though, but the attachments are likely to be specific to each machine and hence costly. Anyway four acres is tractor territory in my opinion
A small tractor with a power take off and a three point hitch at the back can take all manner of attachments from all manner of suppliers. Ebay is full of the stuff. It can also mangle or kill you or demolish the side of your barn cos even a 15hp job will weigh over half a tonne so get a day's training from an ag college - the farm accident stats remain persistently high with tractors a big part of the problem.
It's a compromise. Too small doesn't have the grunt while too big gets in the way.
The market is essentially old machines (MF35 etc from 40 years back), Japanese or Chinese/Indian kit. The Japanese product (Kubota, Mitsubishi, Yanmar, Iseki etc) lasts reliably for ever, so s/h prices can be high particularly for more powerful machines. Lots of them are grey imports though the tide has turned following currency gyrations and there's fewer coming over now. New John Deere and Massey tractors are rebadged Japanese.
If you buy Chinese make sure that you're near the dealer cos there's a reason for cheap. I just sold a 20 year old Kubota on ebay for a lot more than I expected, more than I paid 5 years ago. It was cosmetically scruffy but mechanically solid. The winning bidder was from Dortmund, the underbidder from Croatia (who was replacing a well-known Chinese tractor that had lost 2 of its 4wd and leaked oil)
Old tractors already have lasted for ever and can be a lot of fun (many bits are easily available) if you want an extra hobby. Just remember that health & safety regs didn't exist when they were built so there are more ways to mangle yourself or the kids. And nursing the brute along is all very well but when you've got real work to do and the weather's about to change it's tedious. I like solid and reliable, so my vote is Japanese, new or old.
Don't get a "garden tractor" and expect it to do everything. They are wonderful lawn mowers and really manoeuvre well (I have a JD) but while it will top rough grass very well you don't get hydraulics or a PTO and there's insufficient weight for good grip. Compromises...