Well, for speed and jumping on a track I would take my Jammin X1 CRT, that's on the back right. Nothing will beat that. For speed and jumping in a back yard or rough area, I would take the Monster GT cuz it gets you some extra ground clearance.

There is an easy solution to your clutch problem. Take the clutch spring out, cut of the loop at one end PLUS 2-3 spring windings. Then take the loop that is left, and loop it into the last 2 windings (where you just cut off). Basically, make the spring shorter, thus the tension will be tighter, and you will get later engagement at higher RPMs. See if that helps.