All but 1 of the Phoenix sails has those little "tail" vents (6 total). Someone in our group nicknamed them "quarter vents". They do change the wind range for each sail slightly upward. If all your friends are on mid-vent Revs, you might still be on the std Phoenix, etc. They also make the transition from forward to reverse slightly easier. Still can't jam it on without thought, but it is easier. And they do shrink your wind window slightly.
The Shook feels sluggish???!!??? Mine is just about the "lightest" feeling sail in my bag! Feels way smaller than what it is. Almost like comparing a Rev2 to the 1.5, light and fast.
IMHO - much over 20-25 mph and flying stops being "fun" and becomes a sort of survival. But YMMV ......