I've just recently bought a mk3 16v.
I thought for ages about whether to get a 16 or an 8 and asked loads of people etc.
I drove a few of each fairly hard and i honestly think that this 'huge' difference people are on about is just bo***x. Yes there is more power over 4k in the 16v but its true the 8v has more pull from almost no revs. There is a 35hp difference and a big 'quoted' 0-60 time difference in the books. But driving them side by side - literally getting out of one and into the other for a proper rip round the same roads, the difference is negligable. I think the engine in my 16v is a little tight and needs loosening up, and i know my mates' 8v is nicely loose. So yes, perhaps mine will loosen and will get a little quicker, but who knows.
After just over 1000 miles of mainly commuting, i think i might prefer the low end grunt over the 4000k+ power. Because you dont have the opportunity to use it in traffic. I drive to work everyday and don't often get the chance to use more than 4k revs. That said, i do like the top end power when i've gone for a rip around some of my favourite roads when its quiet, even though it takes a little more concentration to keep the revs high when up and down changing.
I honestly think that given the choice again i wouldn't give a monkeys about which one i got, i would simply buy the cleanest example of either that i could find second hand. You won't be dissapointed with an 8v. It most definitly IS a real GTi.