Start watching some of B team games and then comment. If you look this years performances Muniesa is much better and his big advantage is that he is an all-rounder. He can play left, right or in the centre. On the other hand Bartra is not so "rock solid" as he was last year. He is prone to making mistakes and his concentration is very close to the one of David Luiz.
But yes, looking at past two years they both deserved promotion. JDS is here for the past two years on the verge of promotion so this isn't really a surprise.
I am only feeling bad for Montoya. Guy is super talented and is already a class right back but he will hardly get any chance.
Also, dunno what will happen with Cuenca and Tello. Cuenca could go for free, and Tello will stay probably with B team because there will be less opportunities forplaying time when Affelay and Villa come back.