1st i ride for Airush BUT it was the VaporX that made me change over to Airush in the first place

I cant give you a direct comparison but i can say the Vapor X rocks!!! it has stacks of power! depowers nicely reluanches is good, LOOPS are INSANE!!! and pops fantasticly. i love it for freestlye and i know guys that love it for waves because of the way to steers and drifts back in the window when sheeted out.

If you are in Perth then drop into Airborne Kitesurfing and we can give you a demo

Vapor X will have it all over the Varial in Speed, turning and upwind ability.

Boost not sure, possibly they are similar, but I suspect hang time on a Varial will be better due to the flatter canopy.

ive ridden both but i own a vapour x I would say that the 9m vapour x would probably have same bottom end as the 10m c4.
both very nice kites think you would be happy with either, my preference is the vapour x.