Mekhis's competing with a pre-prime Satele is probably worse than Serra Keto's accolades of being an incredible swordsman, and, alongside Cin, being the Order's "last hope". That, and together with Cin, she's capable of giving Knightfall Anakin all he can handle as per the BTS of the RotS game. That, and she has an unpredictable fighting style, so I'd say odds favor her more than Mekhis.