Not all of those "Big 4" brands have exactly comparable sizes, per their own geometry charts. The decision would not be two of each. The decision would only be one of each. The decision would be from my own "frame of reference" (no pun intended). I would still go Dura Ace and skip the Ultegra because I decide not getting two of each.
My frame of reference is about my own sizing and how I would go to my bike fitter who knows me better than I do, from her frame of reference.