Milltek Cat Back System

Gonna treat myself to the Milltek cat back soon but just wondered if there was much difference between the Milltek de cat and the Milltek sports cat? Sound wise and performance wise?
I was thinking of the sports cat as it's less hassle when it comes to the MOT..
 
I've got the sports cat on mine and it feels fine, doesnt seem restrictive. I haven't got the pre cat in the manifold though so this may make a difference.

If you have the cat in the manifold then I think you will pass an MOT with a decat anyway