Having had an 8v and now owning a 16v I have to say there is no contest between them, 16v wins hands down. However it's more expensive to run (in mpg terms) and insure.
What I will say is whatever you go for you won't be dissapointed, they bothe have plenty of good points. The two golfs I've owned are the oldest cars I've ever had, most of my other cars have been a year or so old, yet the Golfs still feel the best built and most secure. I'd say that the 16v is probably the best car I've had, especially in terms of value for money.