With Mio, being mature, responsible and level-headed when compared to her peers, which I find sometimes really unmatured and annoying to watch for too long lol.
And with Fubuki, Fubuki is usually always cheerful and excited, singing little songs and making many in-jokes. She is shy when confronted with new circumstances, and when embarrassed she "hides" at the bottom of the screen with only her fox ears peeking up. She becomes enthralled in games and has cute conversations with scripted game characters, or voice acts as characters while making effects.
That's why I like most of this two.