[quote=Phobos]
And well I think Arrancars can be considered a different race when compared to Hollows, because the way I see it they're the Vizards equivalent of shinigamus but for Hollows. Since they have some shinigami powers.
[/quote]

Except, Vizards don't happen normally like an Arrancar does. Ichigo is the only exception in this case. Ichigo is a rare existence where he is a mixture of human, shinigami, hollow, and quincy all in one. But, a shinigami alone can't become a Vizard because they don't have the hollow part of them. The Vizards themselves were created by Aizen's experiments. So, Vizards would be even more limited than Arrancars because Vizards aren't natural. But, a Vizard is indeed a race because you have to be born that way while an Arrancar is just an evolution of a hollow. Though Arrancars often are stronger than some Vasto Lorde ranks of hollows, they often come from hollows below menos ranks.