Honestly I dont really know the potential of either one. But from what I remember yammamoto said that Unohana was one of the strongest captains in SS because she was his student. While Baragan the (so called) leader of the Espada hasnt really faught anyone. Letting his fraccion do all of his dirty work. So this would be a great fight to witness.
at this point, i'd say Barragan, definitely.
This fight should be locked, seriously.
We know next to nothing about either of them. This is just a speculation fight.
Unohana has Shunpo that lets her move at Lightspeed
Barragan has City Busting Ceros.
Not much we can go on here...I voted Unohana on a whim.
I voted for Unohana simply because I have never seen her surprised or taken aback by anything at all. Even when Aizen was considered dead she still wasn't surprised and after seeing Hitsugaya done in by Aizen she seemed ready to stay her ground and Aizen just walked off. Also the Arrancars responsible of cleaning up the defeated and dead just left the scene when she came.
It's true however that we know nothing about either of them so this fight would just be pure speculation as stated before.