Ahsoka qualified for knighthood after her battle to prove her innocence. (Windu called it her Great Trial.) but she chose to leave the order instead. And she gained hella experience and dueled some tough customers during the Clone Wars. She showed incredible resourcefulness and the ability to improvise and survive situations where she was in appearance or in fact overmatched. (Ie taking on Grievous.)
Nothing against Ben, but I would predict a win for Ahsoka or else a draw.