Seriously guys, you need to own/drive both cars to make a fair comparison.
I can tell you stock for stock,a GC8 WRX (Old shape) will kill a GTS-T. At high speeds the WRX shape becomes wind resistant big time so a GTS-t will probably win from 140+. Up to there though there is no chance.
Power means nothing, WRXs have good bottom end and punchy little turbos. 0-100 the GTS doesn't have a chance..... Accept it and move on.
This is providing the driver knows how to handle the car. Give a rex 3K feed in the clutch quickly and it cuts. Get it wrong and its over.