Anniversarys keep there value a lot better.
You had multiple specs off the GTI in the uk, going from slowest first:
2.0 16v
1.8 20v
1.8T 20v (what you want)
Then the 1.8T came with slight engine variations, the first batch was the engine code AGU, no VVT and equipped with a k03 Turbo it also had biggest valves, later batch was the AUM which has VVT and a slightly more complex due to the new 7.5 ECU, it also came equipped with an improved K03s Turbo. The anniversary is more or less like the AUM but a new engine code and 6 speed gearbox.
K03 Turbo with a map goes 190-195bhp
K03s Turbo goes 210-230BHP
The AUM has more features you may desire due to the ECU such as traction control, can have cruise control and launch control added as well easily and so on... AUMs have slightly more issues due to being more complex but don't let it throw you off as it is still a very reliable engine. Anni uses the same shizzle as the AUM
Jump on the mk4 section about common problems.
That's a short introductory to get you started and help you decide what you want.u