In Ras Sudr, Egypt, I had the chance to fly a Juice 18.
Wind wasn't that strong, around 15 knots or so.
I had it on the hard bar pressure and slow turning setting.
The bar pressure was too high for me, although I like more. Didn't feel comfortable. But I didn't try the other settings, but I am sure it will be better.
It turns very fast for an 18...I did some handplants and the kite fully looped, which was nice and fun.
The lowend is better than the Rebel 18. No idea about how end, but assume the Rebel wins here, since I was able to hold the Rebel in gusts up to 34 knots during the Big Air Tarifa competition
The lift of the Juice is not as good as the Rebel 18. Hangtime is ok, but the Rebel wins here too.
So, like North already says, the Juice is more for low end riders maybe on Hydrofoils and Wave to have fun. Rebel is just an Airstyle kite with less lowend and more high end. Whoever has less weight and want to ride an 18, this is your chance. For heavier riders the Rebel 18 is fun in a bit stronger wind.
I hope this helps