Let's ACTUALLY get some good info about the both of them.

statistics

Seymour- final HP 80,000
final defense-180
final magic defense-100

Seifer final HP-34,5000
final strenght-estimated at a little above or a little below 100
final magic power-barely 100

personality
Seymour-cool and calculating

Seifer-hot-headed and impulsive

background

Seymour-Twisted by the darkness of the world, granted power by his mother who turned herself into a Fayth which called the aeon Anima. Kills his father and becomes a Mastier of Yevon.

Seifer-grew up in Edea's orphange until being transfered to Garden. Gifted but incapable of taking orders.

Endings

Seymour-Fainal Battle in Sin. Turns into Omnis in order to kill you so he can control Sin. Unfortuanately, he summoned to much mystical energy and he did not have enough energy to dissapear.

Seifer-Final Battle in Lunatic Pandora. He tries to stop you. He has no real goal. Just a warrior and a puppet Ultamecia uses to halt your progress.

With Protect and/or Shell, Seymour would reduce Seifer magical and physical attacks to 1,000 AT BEST!

Seifer loses. I will be deeply shocked if Seymour doesn't win. Especially since I'm the only one who's given a good arguement either way.

To WetWired: So Yuna and the other beat him 4 times. If I remember correctly Seifer was defeated a total of four times. Even if he wasn't at full strength the one time. The bottom line is Seifer could not win because he doesn't think things through.

Seymour Wins!!