My Landpride has proven to be a durable piece of equipment. About a 50 inch tiller should be a good match for your tractor. I first used mine on a B6200, it was plenty for that tractor, was a good match for the B7610 I had up until last winter and is a bit small for the B3030, mostly because it doesn't quite cover the wheel marks. I offset it slightly on the 3pt so it covers the track on one side and just work to that side. I don't use it enough any more to warrant buying a larger tiller.
The Landpride is the only one I have owned/used so have no comment on other brands.
Kubota L3830GST, B7500HST, BX2660. Formerly: Case 480F LL, David Brown 880UE
We have a HST B7510 with a 60" Kubota tiller, it does pretty good, if you are tilling new ground it gets the tractor working hard, but it handles it quite well tilling 4-6".