Auto-battle drops

Well, I want to obtain UMP Spec in deep dive, but don't want to manual grind. So I want to gain it in auto-battle, but there are various places to get it: 2-3, 2-4, 3-2 and 3-4. My question is: the drop rate in auto-battle is the same in the four of them? Or one of them is best to auto-battle grind?
Sorry for my bad english and thanks!