8 valve is sub 10 secs 0-60 but not lightening quick. Cheaper to run, fuel and insurance wise. 16 valve is quicker (obviously) bit more pricey to own. VR6 is the bollox fast as f*ck, but thirsty, expensive to insure, bit dearer on the servicing costs too. Depends how deep your pockets are mate. Still very reliable the MK3
Mk2's are probably the best GTI but getting on a bit so if you go for one expect a bit more maintenance expense.
Happy hunting!