Errol Kalayci
Contributor
A backplate and wing is more streamlined leaving a clean front with buoyancy along the back which wraps around the tank and promotes horizontal diving. Think of a boat, you do not want all the weight up top which is what happens with a jacket bcd with buoyancy under and to sides of diver with tank up top. Further, the long narrow tubes lend itself to smaller air pockets than big open bladder of jacket, thus wing more stable...hold a bottle of water with your fingers horizontally...easy to balance, take small drink and repeat still easy, take bigger drink and unstable like big air bladder of jacket. When you dive you want to be horizontal as much as possible to give you more drag and thus control during ascent/descent (as well as some other benefits) and as little drag as possible when moving forward or back (horizontal in the water) which also makes kicks more efficient and less damaging to environment. With back plate and wing, majority of weight is spread across divers back to counteract the lung buoyancy vs weight belt pulling lower body down while jacket tries to pull diver up while not horizontal in water. I have yet had anyone that tried a backplate and wing (properly fitted which takes less than 5 minutes) ever dive their jacket bcd again...they like it that much.