SOLDIER is crap, what did it produce? Cloud, a whining jackass and Sephiroth, a whining jackass with a big sword. So Sephiroth could use Supernova, great. One problem though. While he's preparing with all of those flashy lens flares and graphics, Link would just stab him.
Secondly, Sephiroth's "bigger sword" while it may look cool, has no chance against a broadsword. Why? Because those type of swords were designed to take down horses when you have a lot of time to swing. While Sephiroth was gathering up to swing, Link would just stab him.
And finally, if you're going to debate something, actually debate it. If you're just going to type in all caps "SEPHIROTH WOULD WIN U R DUMB" then you only prove yourself to be a jackass.