ok im gunna go against what u said previously about ff7 SUCKING :O to shame. fine 8 was great but ff7 ruled by far (i mean why else would they make a film, new games (crisis core, dirge of cerburus, before crisis and rumours of a remake of 7 WHICH WILL OWN) AND an animated episode named last order to explain zacks bg (which is seen in the game ayway but still......)) sephiroth has a kick-ass HUGE sword aka masamune which doesnt draw blood (square came up with the idea tht becoz they couldnt create good enuf graphics for the blood when aerith/aeris was killed they made it so they seph's sword was magically crafted so it couldnt the things we leanr hey????) is light weight for fast manuovering and also.........hes just generally taller than him (refer to booklets Squall: 5"8......Sephiroth: 6"2 ) fine ok the last one dont really count coz seifers tht tall too......but still a point. also as was meationed by someone else SUPERNOVA!!!! ultimate finishing move.....oh and btw another thing.......sephiroth has accesss to ribbons in his game (morph a tonberry i believe) where-as only japanese squall can have ribbon becoz u need a pocket station to get it. and also the materia thing......knights of round.....(ok he dont have it but im sure cloud could lend it to him....) final attack also with phoenix (much more reliable than ff8's phoenix huh? ) and finally last but by no means least.........he has a theme song.....OH YES!!!! one winged angel ffac style playing in the background....squall wouldnt know what hit him. MWAHAHAHAHAHAHAHA
Based on pure skill and experience, i would say that Sephiroth would win. But Squall's unique weapon, as well as his limit break, would even out the odds.
Although, even though I really want to say Squall, I can't deny on how powerful Sephy is. He'd definetly put more pressure on Squall.