A chase begins when the killer commits to pursuing a survivor who is aware of them, and ends when the survivor is downed or escapes the killer's attention. In the base game a chase has mechanical consequences - certain perks and powers only work during one.
In competitive 1v1 the chase is not part of the match, it IS the match. A duel measures exactly one thing: how long each player survives a chase on the same killer. The player who lasted longer as survivor wins the round.
That framing strips away everything that normally muddies a comparison. There are no generators, no hooks and no teammates, so the result cannot be explained by anything except how the chase was played.