Get the STi. You won't regret it.
I owned a Forester before my STi. I found the rear passenger space to small to take 4 men any long distance (ie skiing/fishing trips). The outback is wider and longer but not as tall. I find the capacity is more useful.
Don't buy winter tires and rims from the dealership. Get them on tirerack, or locally.
I change my tire myself (winters to summers). And tell the dealership whenever I get the car service not to rotate my tires saves me about half the price on a regular service.
Overall subarus are awesome cars, great value, and they last a long time. I highly recommend them.