I've never owned a Forester, and had a 2008 2.5 turbo stick-shift Outback. But I've driven recent (20016 and 2017) both Forester and Outback as rentals while travelling. And my wife considered both for her new vehicle in 2017.
Offroad ability aside, (since they both are adequate for 99% of situations unless you are in serious rock crawling country or overhangs are a consideration) I have one suggestion when I know people are looking at both models: Drive the Forester first. Take your time, get a good feel for the car, figure out which model you like, and decide if you want to get a Forester. Decide first, before ever even looking at an Outback. Because if comfort, amenities, ride quality, etc. are any part of your consideration, once you get in and drive an Outback, the Forester will not be on your list any more.
Forester is built on a modified version of Subaru's economy car, the Impreza. The Outback is built on a modified version of Subaru's top of the line Legacy sedan, and the differences are immediately apparent.
I really like my 4Runner. But I sure do miss my Outback, and one would be at the top of my list if I were buying today.