Regarding the Speed 5, forget it. All 3 generations of Sonics are better for hang time, wind range, turning speed and even relaunchability. But I'm sure you know this.
Momo 13 comment in another thread:
Having both Sonic1 11m and Sonic2 9m and using them both for freerace hydrofoiling and freeride/big air on TT, I also find the Sonic1 better for TT for boosting. Good point of Sonic2 is that you have less tip tuck and colapses, so you can avoid droping your kite in the water, but weak point of Sonic2 is that its turning radius is larger and it keeps more power during a abrupt turn, so it's harder to do a nice boost, I tend to feel overpowered quickely.