If the best argument for vBulletin is that it's overkill, then my argument is that you just don't know what to do with it
And if you're going to complain about the heavy load, optimize your design. If you want something simple and to the point and without room for expansion.. Then don't use vBulletin. Heh, just my two cents.
I agree they can work a bit on simplicity and less complication, but once you learn your way around, try to see if drupal can compare then.