Stick with the 3G, no question. It's lighter, uncommon, and can still take any (normal pattern) B-series engine. It also has a proven race history that the other generations really don't. Not to mention it is cheap to buy and work on.

If you want to be normal, sell it and get a 5G. If you want to be a little more unique and have a more modern suspension, get a 4G. If you want to be cool, keep the 3G and make it into a super-sleeper. It is very possible. I have already heard of one B20/VTEC 3G, that's an insane car.