It's simplified. By having 3 weapons to be chosen by 3 diferent stances, you make weapon cycling easier and to some point, more intuitive.
So, having the rest of the weapons on the d-pad makes the player need to use it way less constant, since you'll only need to cycle about one weapon(since nobody will cycle both angel and devil weapons at the same time), while having 3 already "on-hand".
But as a said, this system is not necessarily an improvement as much as it is just a new system. You get more weapons to use, but a smaller move-set for each.
Is not worse than before too. Just diferent. I for one, did not felt the need for a new system, but since it works, I go along with it.