We've been Cat 6 on Deck 6 and Cat 5 on Deck 7. There generally isn't any appreciable difference in the Verandhas.
The biggest benefit to being on Deck 7 over Deck 6 is that there are fewwer Inside Staterooms (Cat 11) on Deck 7 compared to Deck 6, so you would expect less traffic (i.e. noise) on Deck 7 than on Deck 6.
We have not tried Deck 5 (Cat 6) but want to because of location relative to theater and Resturants. Seems like that rear section of the ship should recieve VERY little traffic and I would expect it to be some of the quietest sections of the ship (can others with experience confirm or deny this?)
We had booked a Deck 5 (Cat 6) for our next Cruise, but we changed our rooms when my brother and his wife decided they would like to join us on our trip and everyone wanted ajoining cabins.
If what you want to concentrate on the differences in verandahs, there are really only four different types of verandhas.
1. Standard Plexi-Glass
These make up the majority of verandahs. The railing of the verandah has a sheet of plexi-glass to deter people from climbing the railing.
2. Metal Verandahs.
These are the verandahs towards the very rear of the ship. Rather than plexi-glass covering the railing, the railing is a solid sheet of metal. Pretty much kills your view of the water while sitting, but many of these verandahs have more square footage than the average verandah because they are located where the side of the ship is curved. So the narrowest part of the verandah will typically be about as deep as a standerd verandah but the other side gives lots of extra room.
3. Navigator's Verandahs
There are the verandahs that seperate the Plexi-glass verandahs from the metal verandahs. All of them are considered Cat 7 regardless of what deck they are on. They are almost totally enclosed except for an openning the size of a port hole.
4. Partially Obstructed Verandahs
These are the Plexi-glass verandahs on Decks 6 and 7 that are next to the Navigator's Verandah. The view from the verandah is partially obstructed by part of the ships metal skin that encloses the Navigator's Verandahs. These four cabins are sold at the lower rate of the Cat 7, even though it is not a Navigator's Verandah.