Hello Aprilivy,
The actual height of the deck offers little to the cabin. What you have to look for is what is above or below your cabin. You have to study the deck plans and choose a cabin that is not directly above, below or next to places like the disco, or the show lounge, or anything that would be noisy.
Some people say to avoid the elevators. We've found that, although the elevators themselves don't seem to be bother us, all the people getting on and off, tend to talk loudly.
Being surrounded, above and below, by cabins usually is a nice quiet spot, which is why deck seven on the Conquest proves to be so popular. Decks six and eight are totally cabins.
You might want to take note of what is easily accessed from your nearest elevator. I always am glad to find that our nearest elevator opens close to the dining room door. You may not know which dining room is yours, but you know neither of them is near the bow.
Being on those two upper decks you will necessarily be near the bow, as the rest of those two decks are mostly pool area and lido restaurant. Running back to your cabin, while at the pool might be easier. But probably not any simpler than stepping on those id ship elevators and stepping out, just a few cabins away from your deck seven misd ship cabin.
So there's my advice. If it were me, I'd pick something on deck seven, just a few doors down from the mid-ship elevators.