No. This is not about comparing to know which project is better. That's a subjective issue and I obviously love both projects. This is just for comparing the obvious, well, aside from that fact that the parent project is all about girls and this one is all about boys (and vampires).
Series Mascots
- Poppin'Party and Argonavis
- First bands to be introduced.
Star Motifs
- Poppin'Party's motif is star.
- Argonavis' motif is a constellation (a group of stars).
Kasumi and Ren
- Both are their project's protagonists. Both are the vocalist of their respective bands. However, Kasumi also plays the guitar while Ren finds it hard to learn any instument. (Episode 3 Argonavis anime iirc).
- Both were searching for that "something" they have experienced during their childhood. Kasumi, for the "Star Beat" she heard, and Ren, for the outdoor live show he had watched.
- Betadori Kasumi is similar to the shy Ren.
- Kasumi formed Poppin'Party (tho the other members were initially against it). Ren was hesitant to join Argonavis.
Rimi and Wataru
- Bassists.
- Both learned how to play bass from their older siblings.
- However, Rimi adores Yuri while Wataru dislikes Kenta.
Hina and Rio
- Geniuses.
- Both has the ability to excel at everything.
Gothic Motifs
- Roselia leans more toward "Elegant Gothic Lolita" motifs.
- Fantome Iris is a Visual kei band with vampire elements.
Hard Rock
- GYROAXIA and Afterglow. Tho former is a real live band, the latter is a game only band.
- Both give off rebellious vibes. (Not necessarily rebellious members tho.)
- Afterglow's members are tightly-knit childhood friends. GYROAXIA is more dysfunctional due to Nayuta's dictatorial personality.
Yukina and Nayuta
- They start out similarly enough: cold, uncompromising, and willing to cut off bandmates if they don't live up to their high standards.
- Both has musician fathers.
- Yukina initially formed Roselia to make her musician father perform again. Nayuta hates his musician father for abandoning him and his mother and he formed GYROAXIA to get revenge.
- Tho Yukina started out as cold, she at least treated her band mates professionally and complimented them when needed. She was also caring to Lisa who was her childhood friend when the latter joined Roselia. Nayuta outright dislikes and doesn't care for his own bandmates.
Childhood Friends Band
- Afterglow and Fujin RIZING! (Well, almost. Yamato didn't grew up with the rest of the members of his band.)
Happy-Go-Lucky Bands
- Hello, Happy World! and Fujin RIZING! (they both have exclamation mark in their band names too! owo)
- Both band specializes in energetic music.
- Both have colorful and fun motifs.
- Both of their leader/vocalist have a positive outlook.
- Both of their guitarist are enthusiastic about their favorite things. Kaoru for her love of Shakespearean works, Yamato for his love of music. Despite their enthusiasm, Kaoru often misuse Shakespearean phrases, Yamato's guitar skills are still pretty shoddy.
- Both group has a straight man: Misaki/Michelle for HHW, Aoi for Fujin RIZING!
EM Bands
- RAISE A SUILEN and εpsilonΦ
Twins
- Sayo and Hina, Haruka and Kanata
- Sayo and Hina are from different bands, Haruka and Kanata are in the same band.
I may have missed some, but will add/edit this as necessary.
Toodles!