Vocaloids
KAITO
Though he was released before Hatsune Miku, Kaito's popularity didn't really boom until after Miku's release, when she sang a Higurashi no Naku Koro Ni parody with lyrics about him. After wards, his popularity boomed considerably.
~ His signature item, Ice Cream, comes from the song that made him famous.
~ Kaito is officially described as wearing a white cute and blue muffler.
~ He is preferred for having a "kind, tender, strong" voice.
~ Meiko and him are sometimes called the "Seniors" (Nenchou-gumi)
MEIKO
She is the predessor to Miku and one of the original Vocaloid programs. Her use of anime-style cover art was what made the idea stick.
~ Her signature item is a brand of sake sold at vending machines
~ Her voice fits many songs, and until Luka, she was the only 'mature' female voice.
~ Kaito and her are sometimes called the "Seniors" (Nenchou-gumi)
Utauloids