It seems to me that for the top sailors in the A-Class, the boat is never what makes the difference. Even this year with the drastically different setups the best sailor won. Usually after the first year of development of a new feature, by the second year a few manufacturers have the similarly good gear to sail on (saarberg/fiberfoam masts, ashby/landy sails, DNA/ Exploder etc), meaning that the class progresses as far as equipment but usually similarly skilled sailors have similar quality gear.
I think, like Chris said, learning may be easier w a controlled foil.
But in the end, the highest efficiency and speed will be attained by fixed foils.
Winglets are only able to change the AoA of a foil by inducing drag. it's that simple...
To the crude controlled foil pictured above, I think they have the winglet's on the wrong wing.
they should be on the aft one. Think of an airplane, pitch is controled by the tail wing.
Some of this may be true for airplanes, but the dynamics of a sailing vessel are very different. 'Winglets' or flaps on hydrofoil craft actually change the AoA/increase lift by increasing camber- which does often increase drag but not in the way you mention, and an automatic way to my eye would be much more efficient than the current 'human powered' system used on kitefoilers, which also increase drag when lift is increased.
In addition, 99% of fully submerged sailing hydrofoilers have had the flaps on the front wing, Bethwaite's canard 49er foiler(which met with lackluster success) is the only craft I know of with the flap on the rear wing.