A combination of greater displacement lift ( due to greater volume) and greater planing lift ( due to more area)
The two kinds of lift are planing and displacement lift, these occur in varying proportions but both are always present whenever the board is moving.
The board does not have to be 'planing' ie.e leaving the stern wave behind in order to produce planing lift, planing lift will be produced even at paddle in speeds.
Also the amount of planing lift produced by the board will not only depend upon speed but also on the angle of attack, thus more nose rocker for example will produce more lift at a given speed. It will also produce more drag in order to produce that lift, but in reality the greater lift can mean that the board takes off earlier, thus lifting the nose area out of the water, thereby reducing drag.
So a board with greater area and/or rocker in the nose will have greater accleration on takeoffin many cases. Often we hear about low rocker making the board faster on the takeoff but that's only true in some situations.
