JCW or Dinan S2

I bought an 06 Cooper S a couple months ago and I want to put a tuning kit on it. I don't want to void the warranty so my tuning options are limited to the JCW kit or any Dinan products. I was wondering if anyone has experience with the JCW kit or the Dinan S2 kit, which one makes more power? What is your advise? Thanks.

Don't know too much about the Dinan , but the JCW is VERY impressive with very noticable improvement.