>>42762923 (OP)
I'd say she's neither.
Best pony is either Luna or Dashie. Twi is more of a function: a perfect protagonist, somebody designed to be confused by everything and overcome her limitations.
I don't remember the late seasons well, but as far as I do remember, her proficiency at her new job was never throughly explored no, G5 was not real. The only thing I can think of is she was big on universal education, that's cool. The worst pony princess, if we have to name one, is Sombra.