Honestly I think an R32 would have a good chance of being serviced and looked after more thoroughly than a 2.8 4motion in the same car; it is an enthusiasts car vs just a high end car (in its day) so IMO more likely to have had the oil changed at the right time etc.
BS. They are both just as likely to have been well looked after or abused.
There is a mk2 Golf GTI up on a local forum to me, with a 1.8T conversion running the mk4 ECU etc... So a well thought out conversion by all accounts. And it does look very nice. At £3k I can't imagine it loosing ANY money, at all, ever. So long as it's kept on the road.
My money would go on something like that. Most of the other suggestions above are still on their depreciation curves. Go older, more (as much as I hate using this word) "Scene", and your money should be relatively safe.