Ahsoka, quite handily. By season 1, Ahsoka had already tested her mettle against the likes of multiple Magnaguards, Asajj Ventress on two occassions, and General Grievous. All of whom were serious threats to Jedi Masters and even members of the Jedi High Counsel. Season 3 Ezra has, what? Lost to a few Padawan/Knight level Inquisitors? Honestly, there's little reason to believe Ezra's skill with a lightsaber had increased much between seasons 2 and 3, as he was no longer facing Inquisitors on a regular basis. If anything, his combative showings in seasons 3 and 4 seem even worse than in season 2.
The only edge I see Ezra potentially having here is a Force edge, due to his flirtation with the Dark Side and training with a Sith holocron. However, by the end of season 3, he no longer even used what he learned, as he saw how dangerous the Dark Side was in the first episode of the season.