My guitar player and I got into an argument today, and I'm looking for some information to settle the dispute. I am considering going back to standard tuning, while he is going to stay downtuned. He says that if we are not in the same tuning, there could be intonation issues. He basis this on the notion that if our open notes are the same, our intonations will "tolerate" slight variations, as opposed to having different open notes, which will make our intonation more likely to be off from each other's.