I haven't sailed a Futura, but I have an iS 111. When I was deciding what to buy, I was torn between the two boards, but finally decided to go with the iS because I already had a 105 liter bump and jump board and felt the iS would be better in lighter winds altough its volume was 108 liters. This turned out to be correct. I use 4.5 - 6.6 sails on the 105 board and 6.6 - 8.4 on the iS.
I weigh 77kg. No doubt that the iS will plane earlier, point higher and run deeper than the Futura because of the tail width and bigger fin. The iS boards are reasonably fast, but are rougher in the chop than a board with more V in the bottom and a narrow tail. Also, the outboard foot straps on the iS take some getting used to. The front strap is easy to get into, but the back strap can be a challenge.
I think the iS boards are better suited to advanced & expert sailors. Intermediate sailors will have more fun on a Futura, but will not plane as early.
Even though the iS 107 and Futura 111 are close in volume and have the same width, they will perform somewhat differently, but not as much as my two boards.
I hope this helps.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.