New features in Hatsune Miku: Project Diva 2nd include more costumes like Little Red Riding Hatsune Miku and duets. “Magnet” and “Romeo and Cinderella” are two of them. Other Vocaloids such as Rin and Len Kagamine are in the sequel too.
Doesn’t seem like Sega made any major changes to the Hatsune Miku: Project Diva formula. But, that’s probably fine with fans. The first game, after all, was stellar.