If you're talking stock-CLASS autox (which allows r-tires, front sway, filter, cat-back exaust, and struts), the WRX is faster. That's also why it's in D-Stock running against the Type-R, 330Ci, IS300, etc, while the SVT is in G-Stock running against Celicas, Civic Si, 2.5RS, etc.
Out of the box, yeah, a previous poster is right, the SVT _might_ get the edge due to the ContiSports vs. the RE92's. But put the equivalent tires on the WRX, (without any other mods on either car) and I believe the WRX wins on index (and definitely on raw time).
Don't get me wrong, the SVT surely has better handling "feel", especially at 300 lbs less. But it's substantially down on power, and without a limited slip differential, it has trouble with early application of the power it does have. I've also heard that it can't get enough camber legally. It is a bargain at it's price point, but then again, the WRX is a bargain at it's as well.
Please realize, neither one is "the car to have" in their respective Solo II autocross class (but the WRX is the car to have for Pro Solo).