I personally dont think there is any difference between superlift, rough country, sky jacker ect. They all look the same and probably are the same quality. CRAP!!!!!! 
I ran a Superlift 4.5 inch lift on my 85 for several years and several week long adventures to Moab. The front springs performed well and the rear springs were really stiff as expected from the amount of arch required on a stock length spring. I heard that they front springs snapped soon after I got rid of the truck. I wouldn't be scared to run another set of Superlift.
My friend ran some SkyJacker springs on his Blazer and they also performed excellent for him. Great ride, decent flex and he never had any problems along the way.
The biggest downside to either of these brands are they are designed to maintain the stock load capacity which makes for a stiff spring when combined with the additional arch.
