Used both FTT's and JSB exacts in my .20 Hw100 and for my gun the JSB's win hands down.
The FTT's had loads of damaged skirts ( could of just been unlucky with my 15 tins ) and rubbish accuracy compared to the JSB's.
Best Buy some pellet samples to see what works best for a particular barrel .
The .20 JSB's love shooting shot gun shells (used ) at 100 yards ( indoors) the FTT's struggled at 50 yards. I now have only one pellet type in my gun room as I'm a one gun man.