Everyone's just interested in what their type is interested in :P. The perception doms want to know about primary/auxilary perception. The judging doms want to know about the primary/auxilary judging.
I *do* find it easiest to determine --XX, first just because that's how I think. When I meet someone I want to know what that they're thinking and their yes/no, good/bad, true/false process. (And someone who withholds their opinion is of little use to me at all.)
However, I think I would use X--X the most. In my mind I can see the general sort of attitude that person has towards the world and their general pattern of interaction.
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"In their youth, no one realizes that the trees that stretch into the sky are, at the same time, sending their roots deeper and deeper into the earth." - Noriko Ogiwara