When I was very young, my favorite used to be white chocolate...I guess that was just for the novelty, because I didn't expect chocolate to be white, so of course I had to have this strange thing as often as possible.
Later, I used to like milk chocolate because dark chocolate was too strong and bitter for me.
In my early and mid 20's, I got cravings for sweet dark chocolate... milk chocolate is too un-chocolatey for me, even though I still like milk. Only dark chocolate seem to make my whole body feel the effects of chocolate, more alertness, just this deep bliss--and, I'd like to think, the antioxidants at work.