Folke said:BUT: Every methodology that is based on using lists or notes also implicitly uses the "out of your head" premise, even in those cases where they do not emphasize it or even mention it.
Yes but GTD is the only approach I have ever encountered that suggests you should get everything out of your head that means something to you. I'm not saying you are wrong for liking or identifying with another part of the system personally. But in terms of what makes GTD different, the "everything" part makes a key difference and is what sets GTD apart.
Am I wrong? Are there multiple systems that recommend this get-it-all-out-of-your-head approach rather than just writing the "important" things down? If so I am curious as to what they are.