According to Nintendo Power, it can be divided either way for two players. For three players I think one of the players is always going to have more vision unless HVS splits the screen four ways and makes one of those sections unusable. Maybe they will fill it with the scores or something.
Remember those in prison as if you were their fellow prisoners, and those who are mistreated as if you yourselves were suffering. Hebrew 13:3 (NIV)
For three players, I hope they either make all three screens the same size or allow an option to set it that way. When one person gets a half-screen and the other two get quarter-screens, the one with the half-screen has the advantage.
What i think looks the best is to simply put black bars on the sides of the view of the person who would otherwise get half a screen. (Basically, crop the half-screen player's view back down to a centered quarter-screen.)
Help is a gift that one must never grow to expect. -- Willow (Witches' Brew by Terry Brooks)