Scott said:

Particle masses?? Definitely go with Gell-Mann.

But Scott, the fact that you say that, means that if I saw that you were still arguing particle masses with Gell-Mann, the most probable explanation in my mind would be some kind of drastically important modern update that Gell-Mann was bizarrely refusing to take into account. Such an event is not beyond probability.

Gell-Mann is a Nobel laureate and you are not (yet), but you know that, so you would disagree with Gell-Mann lot more reluctantly than he would disagree with you. To the extent that I trust you to know this, your disagreement with Gell-Mann sends a much stronger signal than Gell-Mann's disagreement with you. It doesn't cancel out exactly, because I don't trust you perfectly; if I trusted you very little, it would cancel out almost not at all.

But you can see how, in the limit of disagreement between ideal Bayesians, the direction of disagreement on each succeeding round would be perfectly unforeseeable.