In my opinion, there is a sound difference over OEM, both outside and also in the cabin, no one has ever left saying that it sounds just like OEM... The Milltek can be compared to OEM but the Scorpion has volume over OEM...
The Scorpion is louder than standard, we fit both all the time and both have their merits, I do know of someone selling a used Scorpion system too, which we originally supplied...