Which source so you intend to have dominant? How is the soundboard/soundman at the venue? How chatty will the crowd be? I think most people tend to preference the sbd and use the aud source for ambience/presence/depth, unless the sbd source will be less-than-ideal. I would think putting the best equipment on the source that's going to be favored would make sense. I usually run the aud source 10-12 db lower than the sbd, if I like the board and the person operating it. Depends on the circumstances, though, and ultimately what sounds best in post.