The "best" depends on what you want and what you cut.
Bushhog, rhino, woods, landpride are all some good brands. But they all make light, medium, and heavy duty cutters.
Ranging from a 5' cutter with 40hp gearbox and weighing 500lb, up to 5' units with 100+ HP gearboxes and pushing 1500lbs.
If all you are mowing is grass and weeds, a lighter duty one would be fine. And probably cut better too. Cause the lighter ones typically run a little faster blade speed than the really heavy ones that are meant for clearing brush and small trees.