This is... A bit confusing. Is this a "who do you like better" topic, or a "who would win in a fight" topic? The name suggests the former, but the content suggests the latter.
Oh well. For me, it's the same for both. Sora. He's a more developed character. He has more depth in his short time existing than link has from, well, however many years since zelda was released.
As for in a fight, Sora has link beat in every aspect.
Better magic and more spells (and he has healing spells to cancel out links faeries, pots, lon lon milk, what have you.) He can use spells more often, and more rapidly.
The keyblade is not an oversized house key. It's the key to the secret of all existence. A good bit more important than a sword made to combat something as petty and limited as "evil", wouldn't you say? Also, the master swords attack power isn't anything special because of the way the zelda games are designed. The keyblade has much stronger incarnations. So in both aspects, magic and physical attack, the keyblade wins.
Sora has more abilities than link, including his transformations, all of which are more than enough to soundly whomp poor link. Sora wouldn't even need them, but if he did use them, Link would be dispatched that much quicker. As for links ranged capabilities, Sora is well equipped to deal with that. He'd likely be able to dodge most of Links attacks and close on on him, but if it did come to ranged battle, Sora transforms into magic form and shoot spulses of magic energy like a gatling gun, and oh yeah, he can cast spells with absolutely no recovery time, one after the other. I mean instantly.
Growth potential. Sora gets much stronger as he adventures than Link does. Link gains more gadgets, gains heart containers, and a larger magic pool, but his stats remain the same. Soras stats increase vastly as he levels. His growth potential is collossal. Links isn't even mediocre overall.
Soras special attacks. They would make mincemeat out of Link.
Reaction commands. Since this would be a boss battle, Sora would have reaction commands available. Don't know what they would be, but it just hones the already keen edge Sora has over Link.
So yeah, I reall ythink Sora has Link outclassed.