Performance wise? I think the Sti is the better performer... to a certain extent.
1. It handles a lot better, though having AWD can sometimes be a nuisance.
2. It gets out of the hole pretty well (AWD is good for some things)
3. It's a little lighter.
1. Too much attention is not a good thing... Police love to pick on boy racers.
2. Not enough grunt after it's launch
3. It's a fairly stiffly sprung car, makes for an interesting ride on rough roads.
4. It's nice, but I don't think it has the fit/finish of the GTO. It is kind of noisy, and not nearly as refined on the interior side of the car.
That's about where it ends for the STI.
For the Goat:
1. It doesn't handle too poorly, though the power steering is slow to catch up with quick imputs.
2. It's got a lot of low end torque to pull out of corners
3. Fit/Finish is amazing. Very quiet, very smooth.
4. It gets great gas mileage on the highway (well the M6 does anyway)
5. It can do a BURNOUT!!!!!!!!!!!!!!!
1. In town gas mileage sucks... (wait, maybe I should keep my foot out of it!)
2. Getting into the back seat is a ten minute process.
3. The telescopic steering wheel is cheesy, and a pain in the royal arse.
4. That's about it.
As you can tell, I was really stretching for things to say negative about the goat. Yes, I have many other things that I wish I could change on the car, but everyone is the same way. There's always SOMETHING they would change on any car.
I think the STi is a nice car, it looks pretty darn good, but it really does attract the negative attention that a person needs. The GTO is almost too modest in it's styling (which I love) and it will keep you out of trouble if you want to be.
Hell, I'm driving an '04 Yellowjacket M6 with a new Corsa exhaust system on it. I had one ******* try to race me just randomly driving around town, and I wasn't going to bother. But really, an STi will entice some, whereas the GTO most likely will not.
Here in a few minutes i'll post a couple kill stories of my own.