Okay, so a WRX STi, but what's the other one?

Really, though, I think that you have to compare how much different the performance is, and how much different the usability is. Have you test driven either one?

Are you going to find the STi (I assume) so ugly that you're not going to like to use it?

I guess my point is that you're concerned significantly by both, and trying to determine which is more important to you is a losing battle, and one you're probably going to question a lot, if you make the decision that way.