Turntable mat Sonic differences; cork vs. leather vs. rubber compound

I know there isn't a precise answer for this question but your feedback would be appreciated. There are a lot of differing TT mats out there, all with pros and cons and I've heard both good and bad about most of them. My question is this...

What are your experiences with leather versus cork verses rubber compound mats? I know much of this is relative to the turntable in question but there have to be some general sonic characteristics specific to each. What's your opinion?

(By the way, I'm running a Rega P3 with a glass platter and white drive belt, RB300 arm with and underslung IsoKinetic counterweight, all supported on 3 Vibracones.)