Unfortunately for your theory, Jedi and Sith back then would be no match for PT era Jedi and Sith. And Ventress has beaten Jedi Masters in battle. Bastila is really no match for Ventress.
Which is why we only see the top Jedi/Sith from that era. And as far as which era has the more powerful Force users, it's not about the era but the individual. As an individual the Council entrusted Bastila with the mission to take out Revan. That says a lot. Many individual Force users from ALL eras stood out on their own because of their abilities. Bastila was one. Ventress was another.
But in my opinion, Bastila wins. I won't say it would be an easy win. Ventress is cunning and deceptive. But she also allowed Yoda to yank hger lightsabers from her own hands lol. While Bastila lost hers in a crash I doubt she would let ANY Jedi Master take her lightsaber from her. It's engrained in Jedi that the lightsaber is their life.