>>528488298
Upon conducting thorough research into both of these characters, I have discovered that Serena's cleavage is rounder and has a larger radius but does not protrude as much as Hailey's, giving them an effect that they are bigger when pressed up from her default outfit.
Hailey's protrude further out and have a more natural sag to them giving them a "heavier" and "massive" effect.
I prefer Hailey's.

Hailey also mogs everyone else with her Bunda.