Part of my intention was to let you choose which of those two definitions is stronger in your eyes. Obviously they are both main characters in their own way.
For example, would you say the same thing about FFX? I wouldn't. Tidus is not only the character you control from the start of the game, but the story actually has a very close ties to him, and once you get to the end you see how it deeply revolves around him. I would say he is the main character of FFX without question.
For XII it is a lot different. Vaan doesn't really have any deep connection to the main story, while Ashe does.
This also will be used in an event I have planned later so I encourage people to vote even if you don't feel there was a true main character. Vote for the character you felt strongest about. For me that was Princess Ashe.