Man, you ask hard questions. LOL I have never actually taken much notice on how much "fat" or "grease" drips from either, but just "shooting from the hip", I "Think" I'd put the pork butt on top.The Bark of the brisket is going to be more tough than the pork butt, I think. Also, they both should cook about the sam amount of hours and the pork butt is "fall apart tender" when it's finished, where brisket has more of a hardened bark and would hopefully resist absorbing the drippings from the butt.
This is a suggestion from a newbie, and I'd wait till some real Pro's chime in on this one.
Great question however, and I'm anxious to follow the respones to it.
In my case, I'd cook them separate. LOL
