It's not always easy to put explanation into words, I'll try. I've spent a lot of time on iSonics and a Kombat (mine is 86 lit). Cambered sails are good with boards that have harder, boxier rails and flat rockers. That's because you want maximum acceleration and speed ("efficiency" is the word these days ;-) Pedal to the metal, never sheet out, take no prisoners ride. Cruising comfort, maneuverability and ease of gybing come after that. And you want all these things in ugly chop, right?
So, you CAN use a cambered sail on a Kombat (I've sailed 3-cam Daytona on K86), but it will take away some of that board's playful character. It's not meant to be driven always at full throttle like a slalom.
Better than any explanation, try this: put a no cam sail on your iSonic, and put V8 on a Kombat. Neither is a good combo that will give you a satisfying ride.
Now Ola could offer you his view, as he recently started to use iSonics I think.