Jay, If it's a temporary car, Mk2 every time. The 8v's are still a good car, you can get one for very good money, and probably not lose much. They're fun, pretty quick, and pretty cheap to own.
The Mk3's are lardy, not fun to drive, but do hold their money relatively well, just not my cup of tea.
If it counts any, a Mk2 GTi will trounce a Mk3 any day of the week.