Peope have more success on Testopro. There are alot of non responders on Prime. I have tried both and both have worked. I actually gained have an inch on my arms in the first month I was on the Asteroid stack (No, im not joking) This was coupled with a hard, heavy exercise program (Im an NSCA certified trainer so the program was a large part of this as well) and a solid diet. I than went to the swole stack. Cut me up. Started training in crossfit to cut up for the summer. Kept all my size on the swole stack while doing crossfit. Arms are the same size. And cut up like a mofo. Veins popping in all sorts of place. Both are great stacks/products. I know you want a exact answer but by my personal use you cant go wrong with either.