I have actually sailed both with a 7,0m2 NP RS 2010 - Amazingly it works also in marginal conditions. The iSonic of course is a tad quicker, and has am more uncushioned direct feel. But it is also less comfortable. The futura is just the most comfortable board out there - and still lightening fast. Both jibe extremely well.
The isonic is the most accesable race board i have ever tried - Still I would go for the futura because it puts that great smile on your face in every condition.