Nomi easily.
Firstly Karkko relies heavily on his illusions. Nomi can see through and dispel illusions without effort so that's his biggest edge gone and as we've seen he can't recover fast from any kind of unexpected setback.
Second, while she dislikes lightsabre combat, Nomi has fought in many battles and is an accomplished swordswoman. Karkko by contrast is an absolutely pathetic fighter with practically no skill at all
Nomi Sunrider all the way!