What was your goal in this switch? All four are rear facing cabins at the port corner. So all you have done is move down one deck. Why? As I see it, all four cabins are equal. What are you trying to gain by this move?
Well, I don't know enough about the four rooms to comment on the size of the balcony. If you did your homework and the balconies on deck seven are bigger, then you did fine. At worst you are in the same, just one deck down. I don't consider deck seven to be any better or worse than deck eight for balcony cabins (deck eight is better for the PR cabins).