I think it comes down to taste. I don't care for Outback and the flavor of their steaks and some of their side items. Longhorn Steakhouse has always had excellent steaks and the service has always been great.
I like outback for their appeteizers(sc) but longhorn for their actual meals. Kukabura wings and bloomin onion from outback... Awesome! But longhorn makes a mean burger or anything else. Both are good, but outback is pretty much impossible to get in. Gotta make reservation weeks in advance. At least by my house.