I have had MANY TUBES and toons. One feature I always stress on a tube or toon is URETHANE BLADDERS. They are not effected by temp and Altitude and deterioration. They cost more, but they are stronger and LIGHTER!
It can be compared to one of those sandwich bags with the fold over flaps (PVC) OR the thick freezer bags (Urethane)
PVC stretches, Urethane doesn't. That is why the pay load on Urathane is so much higher.
As far as wind resistance...in a "V" shaped tube you do not notice it any more than a "U". The V seams to make it more stabile and track better. (No floating side to side in the wind)
I started off with an old Caddis Donut (car tube) then got one of the first SFC with the mesh in the back and a Styro seat. Then the Escalade which was a basic SFC with a front and inflateable seat so folded up to nothing.
Then the H3, the cadillac of float tubes, it just don't get any better....no wait, it did. The Navigator II. A nine foot "V" tube with motor mount accessory and OARS. Still folds up to nothing.
I do get a little surprised when I read people wanting to save all the scratch for a FLOATATION devise, instead of their lures, line, reel, rods, even waders. COME ON, this is a SAFETY DEVISE!