So, Vic, if I understand you right, you are saying that Saturn Girl is more phonetically pleasing than Saturn Woman? Or maybe that Batgirl is more pleasing than Batwoman? Or even that Supergirl is more pleasing than Superwoman?
If that is so, then why isn’t Batboy or Superboy more pleasing? Heck, Batboy (Bat Boy?) even follows the alliteration point you were trying to inject.
And before you respond with an age claim, let me point out that in the original X-Men, Jean Grey was Marvel Girl, while Bobby was Iceman (and I think he was actually younger than she was).
The alliteration claim is pretty much a non-starter since the number of male heroes that have names that start with a “M” and the number of female heroes that have names that start with a “G” are comparatively trivial. Any other claim you might consider making has to challenge a thesis worth of evidence.