Is it going to be your only car?
Do you live in an area with Winter?
I would probably go with the STI for a daily driver.
As ugly as the new STI's are, the drivetrain is pretty solid.
The STI is about .3 seconds faster in the 1/4 mile aswell, due to the lighter vehicle weight, and the AWD system giving it a better 60 foot time.
However the Mustang does trap at a few higher MPH, meaning if you could get a good launch, and traction you do have a chance of beating it.
It would come down to a drivers race, with the STI having a slight advantage.
