I would vote for a Mk2 16v too, they're so much fun. I had a Mk3 16v and then got a Mk2 16v and the Mk2 felt much faster and responsive, a better drive IMHO.
But even if the insurance is cheaper on an older Golf, you'll still spend the money you save on mods and servicing. But at least your MPG should be better. I used to get about 40mpg in both the Mk2 and Mk3 16v on motorways.