To be honest, I didn't know there was a dub.
Or maybe, I forgot a long time ago.
I've always watched sub from the beginning because it's the original
And most dubbed animes' voices don't match the animation so it's not any fans' fault.

Specifically, Rosario + Vampire Dub:
• American voices for Japanese people
• the voices don't have much emotions
• it feels awkward hearing them yelp in English
• they all sound similar to each other (I was so sad I had difficulty Dx I'm not supposed to!)
• the dub changes words, leaves them out,
and makes a new sentence instead,
different from the original sentence.

The last one? I didn't notice. I specifically saw when I watched the dubbed version of one episode and the line wasn't even the same as the sub! It was so heartbreaking and awful. I felt sad for anyone who watches dub ; ^ ; It left everything out. It's just not the same understanding. Wouldn't you want to be given the full experience and have it worth your time?

Never mind the language, but pay attention to how the person sounds like without words. When I watch sub, that is their voice. I read the English so it looks like that voice with English words = perfect match! I don't know if you understand what I mean c: Imagine hearing it raw. That's the voice they have, regardless of "gibberish" and change their language to English in your head! ^ ^

Outer Moka-san's original tone of voice is cuter/softer
Tsukune's is softer, sweeter, wimpier, and, when he whines, funnier
Kurumu-chan's voice...fits. Everyone's fits! Tsukune's voice is cuter when he whines.
Yukari-chan's is high because she is eleven. You become used to it ^ ^

Please, I recommend the Japanese dub, English sub!