I am incredibly patient for the reason you mentioned.
There are so many difficult factors to reconcile between the STi and Evo VII. Until more concrete information is released about each of them, however, it's premature to make a decision.
I lean toward the STi for reliability, but the more I hear about REX transmissions, the more I double take at that conclusion. I have had some completely typical wrinkles to iron out with my S4, but every time, the dealer has been great about it. That doesn't sound like the story from the Subaru camp.
However, there will undoubtedly be issues with the Evo VII too. I don't know anything about Pacific Mitsubishi, except, well, they sell s*hit cars at this point.
In terms of performance, once again, until we know precisely what each manufacturer is going to offer, all discussion is just speculation at best.