The size of the scope on the HHA might be a hair larger (I know it's a bit wider, it's oval while the Cosmic is round). Frankly I don't think it's an issue either way, I don't recall either ever causing a sight picture problem.
bowscout....what do you mean "i have the HHA optimizer lite with the Cosmic Impact sight ring". Did you somehow attach a Cosmic scope to the HHA armature? If so how?
Another thing I didn't mention previously is the HHA Optimizer also has better windage ("micro adjustment"
fine tuning. On the Cosmic you loosen the allen screw for the band and you just have to push it. Though, once you have it set there's really no reason to ever have to adjust it again unless you change something in your set-up.