I haven't used the P21S, but heard its about $30.00 a can and I believe thats an 8oz can IIRC. I've heard good things about the S100 from the H-D dealership, but don't know if its the exact same thing. I can speak about the Griots Caranuba Wax in hard paste form though. Its 8oz, hard paste form and smells great and costs $20.00. Its very easy to use and from what the guy at Griots told me, is 33% caranuba, the highest on the market today, thats what he said, but I guess theres various ways of measuring it I guess. It goes on easy and comes off easy, really
I'd like to try the P21S just to see if its worth the extra $10.00 but who knows. One thing I do know is that I have Klasse on the way and one bottle is sealant glaze, so we'll see how that goes. Another option would be to top it off with NXT and because of how easy it is to use, top it OFTEN
and its about $16.00 a bottle IIRC!
but I would like to top it with a Carnauba wax to see if I cah get a higher gloss and show more depth. 
