Watching Gura's stream and I'm sure this is an objective singing power ranking
Red S+
Mori
S
Suisei, AZKei
A
Okayu, Kanata, Towa, Risu, Moona
B
Korone, Marine, Aqua, Noel, Flare, Rushia
C
Choco, Coco, Gura
W
Wallaby
Gura could be a solid B if she doesn't sing like a retard. Her Ride on Time during her debut was far better than what she's singing now because she didn't sing like an idiot.