Neither beat Ami.
Uh what series did you read/watch as actually both beat Ami pretty handily and easily in both formats? In the manga Berthier easily trapped her in a bubble unable to breathe to take her prisoner, while Viluy used her Mosaic Blaster nano attack to take her down all while messing with her head. She had to be saved by Uranus cutting down Viluy.
In the 90s anime Berthier has Ami dead to rights frozen over with no way out and would have completely iced her if not for the intervention of Berthier's two sisters and Tuxedo Mask. (Ami's original appeals to Berthier fell on deaf ears until her sisters came to steal her glory). While Villuy again had Ami beaten with her nano attack and had it not been for the distraction of Moon and the others as well as the attacks of Uranus and Neptune she was as good as dead...
I'd give Viluy the slight nod in the anime since she won more of a combat battle while Berthier basically relied on pure manipulation to pick up the win.