I am jealous that you have your trip booked already~~~you will have a fabulous time no matter what!
Deck Six on the Voyager class is a tad different from the decks above, and only you can decide, along with your travel agent, as to whether to change the assignment. Speaking plainly, if I were in your shoes, I would indeed try to move up a deck or more. All of these decks have a varied amount of different classes of staterooms available. You didn't say which stateroom you were booked into.
On Deck Six, the staterooms with a balcony have less glass on their walls to the sea than those above. However, it may not make that much differece to you. On the earlier "Voyager-class ships", the balconies are "hull balconies", the same as those found on some Princess and P&O ships, as well as some on the Queen Mary 2.
These staterooms do not have full view through the glass from the sky to the floor. On decks 10 through 7, the top portion is open air; the bottom portion is half glass, half steel; on deck 6, the bottom half is solid steel up to the railing.
Google around for broad photos of the ship, and you will see what I am talking about: look closely; it is not super-obvious. Google for other people's photos of the ship; if you check with RCI, they will show you inaccurate pictures of the series. I find that very frustrating. Photos of the Mariner are actually photos of the Voyager....
I know that on the Mariner of the Seas, the 5th and last of this series, the balconies are all glass all the way through to the floor. I know this because I saw her in Nassau this past July while on the Sovereign of the Seas. I took extensive photos of the Mariner for future use.
Having said all of that, please understand that you will enjoy this trip just as you have all of your other cruises. RCI has such a wonderful product out there---it is our favorite line. In my opinion, they take quite good care of their repeat customers.
The Voyager class ships, along with the Freedom class to come, offer such a huge selection of things to do while at sea. If the chance comes though, do indeed indulge yourselves in a trip on the Radiance class ships---they are the "world of glass". All of their balcony staterooms offer beautiful views of the sea, through to the floor.