The 86 is a real legend and I know both Taty and Kevin use it as their high wind board, loving it for both jibes and control. Unfortunately I never used it myself. I have the 76 though, and I use it for kind of freeride/speed sailing (ie no slalom racing) with 5.5-6.6. I weight 70. For that it works very, very well. It's an absolute killer for jibing. The harder you push it the better it carves, I often do thing like full speed carving 360s with it. I think it handles chop quite well too.
Technically, the two boards are rather similar, the 76 having an almost as wide tail as the 86 but less width overall. The volume of the 76 is in real life a hair over 80 liters.
If you're gonna do mostly freesailing, I think the 76 might be nice, but if you will be slalom racing, I would go for the 86.