I have a Scorpion on my machine and its a very well made piece of kit. It fits perfectly and, with that and an Ivan's kit, the bike suns really well.
Nickodemon's quote about Akrapovic being better is interesting as they are one and the same thing. The company originally traded as Scorpion and later changed it's name. So basically, whether your can has Scorpion or Akrapovic on it it has come from the same company.