what the difference between V in tail and double concave in tail?

How would a shortboard ride with V in the tail as opposed to the same board with double concave in the tail? The board having a flat bottom in the first two thirds!

owning and haveing riden all three, on single fins but the principle is the same, concave makes lift, kinda gives the board pop to track up the wave. The V, to me it seems to hold the tail down, here experience is minimal, but its a speed thing bigger waves. The flat, maybe more of a low preformance. But not really, more speed, fine handling in slow stuff, but gets kinda squirrelly in bigger stuff. Tail does’nt hold down, can skip on the drop. That means falling. Thats how i see it

V was a standard design feature in the 70s and 80s. Helps wider boards go rail to rail quicker. V can have a stabilizing effect also and are used on big wave guns.