In the Ki society, we were taught that the fingers pointed the direction of your Ki with the index finger being the predominate one - look at pictures of early shihan and you will see most always have their index fingers extended.
As Chris already stated, the concept of asagao came from DR. Interesting point is that with asagao, the fingers still point the direction of your intent/ki, but since you have more than one finger extended, you can have your intent/ki focused in more than one direction at a time - just my opinion, of course, and YMMV.
Greg