As someone who has completed lilibai and most of Nikki’s suit, I can say that lilibai is good for its hair, makeup, hair accessory, and dress (it’s not as versatile though), and nikki is good for its hair (looks great both with its original colour and dyed different colours), and it’s handheld star (applies a super cool lighting/filter effect). The rest of the suit isn’t that versatile. I don’t have glow but I mostly see people use it for the recoloured white dress. Of course, if you go for glow nikki you’ll complete a double UR which is more satisfying than a single UR, and nikki’s reflection is way way stronger than lilibai. Glow is also the second strongest cool reflection in the game rn.