I never thought about that till now, but as far as I can puzzle together from what I know so far, those which have their core identity in the inside world (some of them are not even human species) tend to see themselves at first glance.
Those who see their core identity more in the outer world, see the body. But still their inner-image and outer body do not match 100% in most cases (age/gender), which causes more body dysphoria if they are out, even if the discrepancy is smaller.