I would put all my marbles on Jinx. For one, he is the second hardest boss of the game (bested only by Time Devourer who seems to come from a Final Fantasy game [and who actually has Final Fantasy music]).

Jinx has Valor Up for defense, and it rasises defense a lot. It reduces damage by like... 80% I believe. He has resistance to every elemental attack (barring water, because there is no water attack in Mario RPG). He has resistance to Fear, Poison, Sleep, and Silence.

Also, Silver Bullet is a one-hit kill attack unless the character presses the A button exactly when it hits. Since Auron is on PS2, there is no A button, so he cannot withstand the one-hit-killing power of Silver Bullet. The only way Auron can withstand its power is with Auto-Life, and he'll have to re-cast it every time he revives to keep up with Jinx.

He simply can't do that, however because, by statistical translation of attributes of characters, Jinx is much, much faster than Auron.

There would barely be a battle.

Jinx

What is it they say about silence being golden?