Yeah, I think there may be a difference of skill or weight going on there. The Cloud has some good qualities, but it doesn't beat the Dyno in going upwind (everything else being equal).
I've ridden Cloud 17 back to back with my 14m Rebel and 18m Dyno. 165 lbs riding Slingshot SP 5'4" x 21.5" in about 10 knots. I'd say the Cloud had slightly more power than the 14m Rebel, but the Rebel sits further forward in the window, so ability to stay upwind was about the same.
I'd be interested to see what the projected area for the cloud. Riding side by side with me on the Rebel my buddy on the Cloud, the Cloud's projected area didn't seem much more than the 14m Rebel (which is much higher aspect ratio and flatter).
As for skill and weight, i am not sure about skill as I don't ride at that spot or with those people. First time. As for weight, we were about the same though he may have been a little lighter than me.
As for the Rebel 14 being close in power with better upwind? Tell that to the guy here that has 2013 10 and 14 Rebel and bought the cloud 17 because he loved it so much. If it had close to the same low end with better upwind, everyone would be riding Rebel 14s in 10 knots which they aren't. That's why they buy the Dyno.
People do tell me that I am a very efficient rider. I could have rode the 14m Rebel if I had my Sector 66.