Oooooohhh That's a complicated question.
Vocaloids are more fine tuned and popular and they have miku while Utaloids are not as perfect as Vocaloids but they are free and anyone could use them and they have teto!
I love teto since I have 2 videos with her song on my youtube but when it comes down to it vocaloids are better even though they are expensive.
Oh BTW, you might like this. [link]