Ventress vs. Quinlan Vos

Quinlan vos and asajj ventress battle in Felucia

Vos.

This has been done multiple times already.

Ventress contended with - and nearly defeated - Anakin and Obi-Wan in each and every one of their encounters. She was literally toying with the former in second duel (until she pissed him off and got her ass thrown off a skyscraper), and technically beat the latter in The Cestus Deception. Vos got tooled by Agen Kolar and Sora Bulq - who are both extraordinary, but not quite on par with Anakin and Obi-Wan - and could barely shake off K'Kruhk.

I don't know. I'm not necessarily adherent to the idea that Obi-Wan is third or fourth in the entire Order. Bulq's legendary.

Isn't Vos a Vaapad master too? If so, wouldn't that help?

no Vos was taught a Vapaad move by Sora Bulq, but hes certainly no Vapaad Master. id also agree Sora Bulq is above Obi-Wan.