I have a black '02 Jetta and the clearcoat is tough...I used SSR2.5 on a green pad, in some areas went up to a yellow pad. Stepped down to SSR2.5 on white and it finished nicely.
I think the hardness of the clear aids in the more aggressive polish finishing nicer on a finishing pad than does a soft clear. This is speculation though...would like to get some real Autopian thoughts on this...