doesn't matter. I prefer Meltdown/Merton (depending on version) with fire absorbing equipment. Plus if you have gem box/thamasa soul you can use osmose then cast the spell. I love using Quick then osmose, then dominating with Meltdown or something. It's just so much fun wiping them out. BUT, that's my #6 character. I have Cyan, Sabin, Edgar, Locke, and Shadow (as Kappa) as my first 5, then Relm as my main magic caster!
(never thought I'd do that but after using her I figured she was best for pure magic out of everyone in the game. I mean sketch is horrible and control is worse, and Celes and Terra can get good weapons to attack, plus Strago will use Lore just cause)
THE JACKEL