Bruce, I wish I could help. I read a book on chocolate a couple of months ago which addressed this very question, but I can't remember the details.

White chocolate includes some but not all of the ingredients of "regular" chocolate; I'm pretty sure that it contains cocoa butter (among other things), but I couldn't tell you exactly what component is missing.

I like white chocolate well enough in some contexts, but generally prefer the brown stuff -- especially dark/semi-sweet (moreso than milk-) chocolate.