Guess it depends whether you want Saloon or Wagon / Estate mate. If you want an Estate you'll only have WRX options on anything later than a bugeye but STI on earlier.
If you are looking for the saloon then I guess it depends on your budget mate. The classics seem to be the same price as older bugeye models and although most of the guys will hate me for saying this now they do look dated. The only exception being the Type R, P1 or the 22b 2 door versions which still look fresher.
The bugeye versions seem pretty cheap although the front isnt appreciated by everyone. Then I guess it leaves the blob eye or the hawkeye but again depends on budget.
An STI has a better spec as standard than a WRX although you can get the Prodrive pack which boosts the horsepower up (remap and exhaust) but you are missing the better intercooler, suspension etc.
Guess it depends on budget mainly mate and what you want to use it for. I have also been looking at the WRX Wagons as its a great car for carrying loads of stuff (fishing in my case) but also enough power (especially with the remap) to have fun in.
There are thousands out there to suit all budgets inc some highish milers for some amazing prices for not that older cars. I would say the WRX Wagons are less likely to be thrashed than the STIs.
If you want an STI though personally I would go for the more modern shapes than the older ones, unless its an import as the rust will be bad especially when driven by rally wannabes
Just my 2p mate and thats only by reading and reading and chatting to people. Give Dunc a shout on Facebook as he tunes them now but obviously the other guys on here. Wasnt a nice one being sold on here ?