As Chazz stated, some of the auto transmission Subarus can have a mod wired in that will lock the center diff. Also, certain models came with a rear limited slip (yes, even front on some-but not ones you would normally use off pavement).
Subaru has made many different versions of it's transmissions, including a model with full time AWD with a lockable center diff. Because many of these transmissions share common cases and other parts, combos like full time AWD, lockable center, and selectable high/low range can (and have been) pieced together. Not to mention, there are transfer cases that can bolted in behind the factory transmission, allowing combos with dual transfer case, 4.44 final drive, etc. *some fab work required.
That being said, a Subaru Brat with a mild lift (4"), slightly bigger tires (27" SSR's, IIRC), and a slightly built stock engine did a lot of the Rubicon a number of years ago. I think they ran out of time, and were unable to complete the trail, but they did way more than any of the Jeepers thought was possible.
My own experience with Subarus is similar, as I often get into places that I should not be able to. No damage, no thrashing, just proper driving. I have owned a JKU, and I think the only place I went with it that my Soobs might have had trouble with was a mud hole. And the Jeep almost got stuck there, anyways. The Jeep has more room, gets worse mileage, and makes a better platform for building something more hardcore. Give and take. The Outback is miles ahead for highway and softroading, has a little less room, and can only be upgraded so far without a lot of work. For most people, that's just fine.