There is slightly more room, it's not a transformative experience, perhaps a 1 cm or two. However if you are a single passenger, the chances are the seat next to you will be empty, it's rare to see these seats in use, and therefore your total room space may be quite good. That effect, however, can also be achieved by careful seat selection of the seating block directly behind Priority, for a lower cost. However if the flight is full, all seats will be allocated, including middle Priority.