Welcome to the new and improved Proflex / K2 Tech Forum!
I can tell you from experience, the fox vanilla R is a lively fun shock...I have read the helix is a much more damped shock. People who like to do bunny hops complain they can't get the rear end to bounce. If you are into jumping over obstacles, or using your rear suspension to launch you off ramps, I guess you may not be happy with the helix.