I agree with the Beekeeper. The front wheels do 100% of the steering and 70% of the braking, and if front wheel drive (like an Outback) about 90% of the driving in ordinary pavement conditions. If it is a part-time system driving the rear axles in normal conditions, I believe that I would still put the new ones on front for best steering and handling, and to minimize hydroplaning in heavy rain or treadworn pavement.
DO consider rotating front to back and back to front, staying on a side, every 5000 to 7000 miles to even out the wear induced by the front axle and steering. I would recommend not switching sides with radial tires, they become accustomed to rotating generally in one direction, and changing rotation may result in belts loosening. This was a big issue back in the late 60s and during the 70s and 80s. My tire dealer says "no problem" to swap side-to-side, but I remind him that he sells tires.
The Outback AWD drive system provides about 90% to the front in normal conditions. If wheel slip is sensed, additional torque is shifted to the back axles by the transfer case. My 77 yr old mother's 2000 OB is a wonderful snow car.
Noah