Yes I had the F93 and now have the I86. I got the F93 as I thought it would be a no brainer over chop, and it was, sort of like autopilot.... I have sailed the F93 in 5.8 weather, with .5m + chop and it was fine. In those conditions I found the Futura a little tough on the back ankle as the deck was so flat, and consequently a little too much foot steering from the back foot. It looks like they have put alittle more dome in the rear of the deck for this years model. However it planned off redicously early and had great 2 sec peaks. Very easy to quick on the Futura.
The Isonic 86 I reckon planes almost as early as the F93 (say 14 knots ish) with a 6.7 RSR. To answer your question I have only sailed the I86 so far with a 6.7, and 30cm-50cm chop. To my amazment I feel it handled it better. I think this is for a few reasons:
more comfortable back foot
narrower through the middle and tail
more suited to the race sail
I found the acceration a little quicker, and according to the GPS, its faster, and holds its top speed for longer ie. the 100m and 250m times.
Overall its a little more exciting to ride. Great board.