In (A) the difference of ranks is equal: in the first round it's 4 = 5-1 = 7-3 = 6-2 = 8-4; if any player defeats the higher ranked player then in the 2nd round it's 2 = 3-1 = 4-2 and in the final it's 1 = 2-1. The pairing in the first round is the same as in the Swiss tournament system used in chess.
In (B) the sum of the ranks is equal: in the first round it's 9, in the 2nd round it's 5 and in the final it's 3.
I think (A) should be preferred since ANY seeding favors the good and (B) goes a little bit too far in my mind.
Which of these two possibilities is used at backgammon (or e.g. tennis tourneys)?