Definitely like the blonde girl's cover the most. I'd even listen to it over the original. KickHim's link was pretty good, but other than the fact that she has a sweet voice, the cover as a whole isn't really anything special. The blonde girl has way more skill, and really owned the song.
Plus, dance, baby, dance was cute
Edit: when the girl in KickHim's video talks at the end, it totally ruins any goodness in her cover. Ugh. Can you play up the "I'm such a cute sweet dumb little girl" act any more? Blonde girl definitely seems to have more personality, as well :P