We normally book the Cat 9's on Deck 2 (prefer mid-ship but would take forward or aft as well. Love the location, quite easy to get to everything. Some feel the higher up the better on the ship but that stems from long ago cruising days when steerage was in the bottom of the ship...that is not the case any longer. I like being close to the water when I look out my porthole.
Cabins would be identical...the only exception would be the cabins on Deck 1 of the Magic and Wonder have 2 smaller portholes versus the Cat 9's one large one on Deck 2 and above.
MJ