I honestly don't like that argument about the difference between electricity and "mana-produced lightning." To me, a thunderbolt is a thunderbolt, no matter how it's made. So scratch that argument for me.

What I did see in this battle though, was how Senesia explained Sigma's significant advantage over Seymour. Seymour is mainly a spellcaster, and Sigma is resistant to elements. No matter what else I heard in the battle, nothing else was as convincing as this. So there's why I made my decision.