RE: iSonic 94
It really depends how much scope you see to use the iS87 in hi speed open water racing/blasting etc. If you've got a lot of hi wind open water action, then for those days the smaller iS87 will be a very nice and competitive solution, far more open water and full race capable than (any) dedicated speed board can be in those circumstances.
But if you are almost exclusively flat water speed (in hi wind slalom conditions) then the iS101 will take you very close to the point at which you could climb onto Missile S.
Rationale here is Missile S range for pure speed really starts from 20-25+ kts (rider/location variable etc), which is also about the start of the real action window for iS87 (open water).
Don't want to discourage you on the 87, it's a pretty epic ride in the right stuff, but depending more on your usage/ride style/water conditions, there may be significant overlap to Missile S by wind range.
Cheers ~ Ian