My original answer would have been the shape of the face, but you discarded my theory saying you are a combination of all three. My next best guess would be the position of your face when crying. I have noticed in two different girls, when they are leaning, even if just a little bit, the tears fall from the eye directly to whatever is below them, I have tears fall on chest, thighs (when sitting) table, or straight to the floor, and when they are leaning on me I feel them falling either on my shoulder or my neck.
Interestingly, one of the girls mentioned above, when she has her face straight, her tears roll down her cheeks all the way to her chin, sometimes falling from her chin and sometimes they continue to roll down her neck. So I would discard the skin type 
And yes, it is really interesting, I also have been thinking why do tears sometimes roll fast down the cheeks and sometimes slow, even though on both cases it has been intense crying with a lot of tears.
