If its small to medium chop then the F93 is a lot smoother. Most likely because it has more 'v' underneath, the board is thinner at the back, with thinner rails, so it gybes easier as well. If its very large chop then both boards will bounce around. Perhaps the edge going back to the I86, simply because its smaller as you say.
I had a F93 and then went to I86, as I found the Isonic more excitng to ride, the F93 was more on 'autopilot' so to speak.
As to a smaller Futura,, I would get one for sure if they made a 80-83 something litre. I would like 58cm wide and 35 tail! Now that would rock and roll in flat and choppy water! I think SB have forgetten about all the 60-70kg guys/gals as well who would like freerace blaster in 20-30knot+ conditions.
I know guys who are 65Kg and can struggle with the power tail of the I86/80 in windy conditions. They need tails in the 33-35cm range.
Isonic 97 2013
JP Speed 50 2014
Severne Reflex 4 7.0,6.2,5.6