I have both the Futura 93 & 133 and often use them my race sails. I also have the Isonic 101. The Furtura’s are fine with race sails and race/slalom fins. But, as Remi said, if you are looking for absolute performance then the Isonic is the way to go.
For general freeriding I would recommend the Futura because it is more comfortable. Slalom races are run in heats so you are only sailing for about 10 minutes at a time where as with freeriding you can be sailing for much greater lengths. Some of my sessions are for 2 hours before taking a break and in choppy water it is much easier with the Futura. Also if you are mixing in any tricks like carve 360’s or helly tacks then the Futrua will shine over the Isonic.