To clarify, I'm not arguing for "X x" over "x : X", I'm arguing for "x : X" over "x: X".
If you had to write it in the form "a: b", however, "X: x" would make as much or more sense to me as "x: X".
If you had to write it in the form "a: b", however, "X: x" would make as much or more sense to me as "x: X".