I'm edging back towards a Quaife LSD to try it out before deciding. I may have to nick borrow Neil's car for a quick comparison.
Otherwise I'll go 4WD in some form.
....All the Quaife diff will do is greatly speed up reaction to loss of traction on the appropriate drive wheel. It reduces wheelspin but doesn't stop it happening completely - That's up to your right foot! It's greatest benefit is in cornering, imo.
Your best bet is to have a go up the dragstrip in someone's GTI with a Quaife (not mine!).