Supersprint is one of the absolute few exhaust manufactures that GUARANTEES improvement in horsepower - and its a fact.
Supersprint has specialized in free flow exhaust systems.
Remus is also adding a slightly improvement in power, but their focus is sound - a deep throath like sound.
Eisenmann is a german exhaust manufacture - they have specialized in making rare/unique systems, like 4 rear pipes, etc.
Simon, a small Swedish manufacture, OEM for some of the german performance houses only makes exhaust systems that adds power, but not in the same range as supersprint.
MK motorsport - they are awesome, heading for the LOUD customers. - It's the closest sound to professional racing you will ever get - banned in several countries world wide.
And then do we have all the styling aftermarket brands, hamann, hartge, ACS, etc - all their exhaust are made by others. Supersprint is the OEM for Hamann and Hartge amough others.
A fact to keep in mind - when purchasing european made parts, such as Supersprint, Simons, Remus, MK motorsport, etc - will you be provided with a 2 year warranty due to EU warranty legislation. (well at least if purchased through a EU based seller)
If I my goal was power would I head for Supersprint - they are truely in their own league. They lead the exhaust market, everybody else is copycatting them.
If my goal was "decent sound" would I go for Remus, thats their focus area, if loud/wild MK motorsport all the way.
If on budget would I pick Simons.