Is 7 star Storm X worth the rank up over the “best” 6 star options?

Squammo

I have Kitty at rank 5 already and was going to take up maybe AA to 5 next, but recently pulled Storm X and have been wondering if I shouldn’t save a bit longer and rank her up instead. Is she a good BG rank up for example?

Armageddøn

Go with storm px AA is a beast even at R4