As people have mentioned the mk5 would win hands down for pure safety and road noise etc. The mk1 would win hands down for handling, and just looking amazing. (I have to say that i would go for a mk1)
Although tuning wise unless something was transplanted into the mk1 there is no way you are going to get the same feeling of raw power. Mine (mk2) is on the heels (and sometimes in front) of the mk5 gti now, and i personally think that my engine is at its limit without forced induction, so there is no way that i am going to be able to keep with a mk5 if it gets tinkered with.
If i had to make a choice of which car to go for, despite all the safety and comfy ride i am a rallye slag at heart so would have to go for the mk1 and make something of it. As much as the mk5 appeals to the safety concious in me i couldn't justify the price and lack of engine noise on it.
final decision mk1 purely for that fact that it is a legend in the GTi fraternity.
