I think you're talkign of 2 things;
1. The engine speed the clutch engages at - 6k or 8k.
2. HOW the clutch engages - this is the 'reverse technique' and I believe shouldn't affect the engine speed. If you've a 6k spring, it'll engage at 6k, etc.
If the engine's 'spooled up', i.e. revving higher, as in the 8k spring then there'll be more power off the line. If the bite is harder with the shoes reversed, I would guess that the 8k spring is better to avoid the engine bogging off the line, BUT I would also guess the wear can be a tad extreme, on the shoes and the clutch bell ... good luck.
Avatar's on form as usual Pablo!!
Al.