Ultima or Fenrir

[Mythological Omega]

Your magic restores a lot faster with Ultima, and Fenrir causes you to lose 1 attack in the chain. Go with Ultima if you're big on power and magic.

 

[pwninator]

I have to say even though Fenrir is slightly stronger than the Ultima Weapon, I still prefer Ultima. Besides its magnificent design, it fits the position much better than Fenrir as the most powerful keyblade in the game. Don't get me wrong I love Fenrir and the way you obtain it is the best but the Ultima Weapon is a classic.