Most stick with the standard 2-shoe without problem.
I've got an Oddified 4-shoe 8k teflon clutch on my MT and a similar Lauterbacher one on my 1/5 on-road.
I suppose it depends what you want to do with the buggy and how much you want to spend.
Personally, unless it's a BARGAIN, I steer away from used ones, but that's possibly just me.
A higher rev, stronger spring will permit a more-sudden engagement for faster take-off, but you may just end up doing wheelies everywhere - basically you cannot steer !!
Standard springs engage at ~6000-6500 rpm, higher rev ones normally at 8000-8500 rpm.
Al.