This question has been tickling my curiosity for a while, and, if I were to make a guess as a male fan, I'd say Starscream and Bumblebee, two famous bots in general, must be rather popular among the female side of the fandom. I've come upon many female fans and creators who seemed to love Starscream, especially his Animated and Prime interpretations, and I recall a girl in high school who was really into the Bay movies and, when I asked her which Transformers was her favorite, she said Bumblebee like her heart was melting. I imagine Bumblebee is just cute to boot while Starscream is a compelling schemer and underdog - as well as fujoshi material with Megs for a niche of the fandom. But that's just my impression. I find those demographic questions pretty interesting, so I'm eager to hear from everyone!