The big advantage is that the cage itself is much lighter so less energy is needed to turn the cage, and more can be used to keep a good amplitude on the balance.
I think that this type of tourbillon, I would call it half-flying, also has advantages in shock resistance as one end of the balance wheel is pivoted in a bridge fixed directly to the plate. (as opposed to pivoting in the cage which is pivoted in a brige on the plate)
And of course there is no cage to block the view of the balance, hairspring and the escapement turning.
I love it.
Don