Jojo has an incredibly coordinated lyric mezzo soprano.. She supports notes better in the 3rd, 4th, and lower 5th octaves (her B2s are audible)..her head voice is connected to the modal register (moreso than Tori's) and Ariana's disconnected falsetto doesn't count..Her head voice is also very colorful, rich and fuller in dynamics.
Ariana is a overrated pop mainstream vocalist.. Jojo is the underrated soulful crooner (her musicianship and expressive stylings are very "soulful") and Tori gives me indie acoustic dream..
Jojo (technically better than Tori, although tori has more musicianship) > Tori >>>Ariana
Ariana is easily the worst vocalist in this group.
JoJo > Tori > Ari
Tori and JoJo have fuller, supported lower registers. They also support in their belting registers higher than Ariana does. They have the ability to emote and enunciate. They can execute complex runs and riffs with more accuracy and clarity. They have more power and overall better musicality.