Hey Secret do you ever sleep?
Don't sell yourself short, what you are gaining in one hand may be removed from the other. The higher up the list, the better your life will be. But remember a merged seniority list is a double edged sword. Somebody may want what you already have.
There is no fair methodology, every permutation and combination has already been tried. It is a point for negotiation, just ensure that you have a better team, has watching Ally McBeal taught you nothing?