If you buy an 8v you'll always want more power and be disappointed that you can't tune it much. If you buy a 16v you'll like the top end power but you'll always wonder where the low-down grunt is 
Someone was bound to say it. But according to some power curves posted on here years ago, the 8v and the 16v have the same grunt low down and it's only when you get to 5k that the 16v starts to pull away power-wise.
Anyway, spec wise, you can find 8v and 16v models with the same interior and exterior options, most will have ABS, electric windows and mirrors, but not all cars had air con or leather seats. Early models may not have air bags though I'm not sure.
As for which engine, the Mk3 is a heavy beasty, so I'd go for the 16v, it won't be that different fuel efficiency wise (unless you're lead footed), so the main difference will be cost of insurance.
Welcome too.
