Boosted Falcon

Whats the difference with single stage and variable shift kits?
And is one better then the other or do they serve different purposes for each setup?

Variable lets you choose how hard you want the shifts. Single stage is just on or off.

Id go the single stage. I leave my variable one one flat all the time. never gets turned off or turned down. Once you turn it off you realise how homo the shifts are standard.