Looking at Strip and votex I think those figures sound wrong but what to I know. I dont know how to work it out either, but I do know that 90% of the mass of vortexs disc is on the rim and strips is evenly distrbuted. Going off the size of the discs i would say if the speeds are true they are very even in power. I wouldnt say that its 2.5 times the power of vortex.

Prove me wrong.