Well for starters their the same but different because one they both have signature summons and play using duel disk also they are made by the same creator i think. different because they have different people, problems and ways of dueling.
But if this was to happen i think between yugi and yusei would win... Then again yugi would win cause he is the KING OF GAMES. If he were to use the god cards he would definetly win!!!
@Zyta: I agree when ever yugi turned into yami yugi aka king ahtim he would win everytime 0_o