I've got the SBX 720 which is lighter duty and Cat I only. However, it is significantly heavier and better built than the low end KK, Howse, etc units. My tractor is at the upper limits of its HP recommendations and I have used it heavily (clay, rocks, stumps, etc) and have had no problems at all.
all that is just to say that Bush Hog makes a good, sturdy BB. You don't mention what size and hp your tractor is but if it is a utility tractor or more than 40 hp then a medium duty blade will probably serve you better and if the price is right, I'd go for it.