All tillers are not created equal. No having said that weight is your friend in the case of a 3 point tiller. You need weight for it to dig. If you going to get one, I highly recommend you check with you local agg dealer and see what they rent. Believe me you will not find any junk in their fleet as they get abused. I tried out a few before getting one of their used ones. More than 60% of new price and hardly used. I wanted to be sure I had the power to operate. I have a Bobcat CT 235 with 27 pto HP and I am easily running a Ansung Terra Force YJR074 tiller. This is a 74 inch wide tiller normally rated for 50HP This unit weighs in at about 1000 lbs and is one sweet unit, built like a tank. As I have hydrostatic drive, I can just slow down and let it work. I can also set it shallow and in a couple of passes at a fast speed prepare a pasture for replanting - used it to skim the high spots off first
On other feature of my Ansung Terra Force YJR074 tiller, is I can set the springs on the tail gate to compress and level the soil behind the unit - not too many out there allow you to do this. Its a great feature to have. I looked at a lot of tillers before getting this one. Also I can get parts - check on that before you buy
First you want enough width to cover your rear tires, if not consider an offset one to cover at least one tire. Counter rotating tillers will throw stuff into the rear of your tractor, if you want that go ahead.
Just my 02, but look at the construction, check welds, and sheet metal thickness. parts availability and if possibly talk to others that have the brand. You pay for what you get and there is some cheap stamped metal parts ones out there.
Keith