MSD Ignition Question

We're in the final stages of getting my motor fired up and we came across a couple of questions with respect to the MSD ignition setup that we have installed. After reading a few posts here, I think I understand things a little better, but I wanted to post this question just to confirm. My previous motor setup had one of the Chrysler chrome box ignition boxes and for some reason we were under the assumption that it was still required. After reading the documentation from MSD and giving them a call, they say that the box is not required and not compatible. If we want to use an ignition box, then we need to use one of their MSD units. So based on the attached diagram, (the first without a MSD box), in order to follow this setup, we would bypass the ballast resistor and feed 12V directly to the coil. The picture was confusing to us because the ballast resistor is still in the diagram.

Assuming that we are correct, what would be the advantage or disadvantage to not using the MSD box (second diagram)?

Thanks as always for your help.