I am sure it is comparable. Considering Flowmaster does not make the converters they use. The tube size is the same. As far as design. The Magnaflow is a much nicer setup. I would bet the converters are better also. They even make a matching down-pipe.
I can tell you. No one has done any flow or HP numbers on them. People have bought and talked about the fit and quality. But that is it. I have done one for a friend on his car. What are you wanting to know?