I've come up with a few VS match ups which I think are equally matched.
This is Round 1: Asajj Ventress
vs Bastila Shan
Ventress was a dark jedi and Bastila a jedi padawan, both strong in the force but not yet masters. But both very powerful and with great potential.
was a master of Jar'Kai and a formidable lightsaber duelist, she was also a powerful practitioner of the force. She fought and almost defeated Anakin Skywalker several times and was able to hold her own against Skywalker and Kenobi combined. Even Sidious recognized her power - fearing Dooku may be training her to overthrow him.
was also a skilled lightsaber duelist, wielding a double-blade lightsaber. Holding her own against Revan, Jolee Bindo and Juhani (although ultimately defeated) as well as Darth Malak - one of the greatest lightsaber duelists of his time. She also had great power in the force, able to master battle meditation.
Who would win?