Missionx2 is BMSG's second audition show, the one happening right before The Last Piece. Although the show is mostly focused on members chosen to debut in MAZZEL, we also meet Kanon here and find out more about his story before The Last Piece.
The First is the first ever audition show from BMSG, where we first meet Taiki and Rui - it shows not only important context for Rui and Taiki's story, but also context of BMSG as a whole and the ideals behind the company's core existence.
both are bmsg audition shows and the process of group formation is relatively similar. i personally think bmsg shows are some of the best audition shows as they truly work towards improving the skills of participants and choosing the ones most fitting to debut in the end.
both are bmsg audition shows and the process of forming a group is relatively similar, although missionx2 follows the story of mazzel being formed after the lineup was revealed to the public already.