Ahsoka, by the end of S1, has achieved both formal training from the jedi-temple in addition to real-life combat experience under Anakin, Luminara, Aayla, Rex, Obi-wan, and so on. She has contended with Grievous, Magnaguards, Ventress, Cad Bane, and countless numbers of battle-droids in various environments.
Ezra certainly has similar combat experience, but is lacking in the formal jedi training department in addition to foes. He struggled against the inquisitors, who were stated to be high-padawan/low jedi-knight level hunters.
A duel between these two would not be decided by their saber skills, though I would give the slightest edge to Tano, but rather by their overall knowledge-base and how they can employ it in combat. I personally believe that anything that Tano tookaway from Anakin is more valuable than what Ezra learnt from Kanan.
Ezra might take a round or two out of ten.