Round 1: Jack he has assassin's rush to get behind him and also he is much faster and more versatile
Round 2: Jack again he keeps his own attributes from the previous fight but combined with the SoA will win despite Majora's superior speed.
Round 3: Jack again as a dragon he can fly breathe fire and bite him. Majora will get some licks in but won't be able to handle Jack's power.
As a villain I liked Jack.