I've used both... the regular comps, and the super comps for the 65-66 mustang.
Both are a step up from the generic brands. The regular comps are made from thicker tubing, and are very durable, while the super comps are made from thinner (lighter) material, and are a little prettier. Both collector outlets on the super comps point perfectly straight back, while the regular comps come back angled a tad. It's nothing major, just a detail thing.
The super comps are a little closer to equal length, lighter weight, and slightly prettier.... and since both have 1 5/8" OUTSIDE diameter pipe, the super comps are slightly larger inside because of the thinner tubing. It's really thin compared to the regular comps. The regular comps are some heavy duty units.
The super comps are advertised to work with the revised spark plug location of the World Product's heads, where the regular comps won't. I don't know if the plug location is changed on the AFR head, but it might be something to look in to. A buddy tried to install a set of cheapo' headers on a Fairlane equipped with WP heads, and the plug wires laid right against the header tubes...
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3