Isonic 122 vs Futura 122,133

I have the option to buy a futura 133/122 or an isonic 122 although the isonic is about half the price.
I am an intermediate sailor weighing 67kg and will mainly be using a 8m or 6.5m sail in winds between 11kts and 18kts in fresh water.

I know that the futura will be more suitable, but is it worth double the isonic?, I have sailed futuras in the past.

How easy is the isonic to sail? The closest board I have tried to it is a fanatic falcon 121, are they similar?

I can just about waterstart and am learning carve gybes

Thanks

Mike