If you are prone to motion sickness, the lower and more center the less motion you will feel. Some feel the lower aft rooms pick up more vibrations and noise from the engines, but the view is worth the inconvienience.
I have noticed that there can be a lot more noise from kids in adjoining rooms and the halls in the lower levels, probalby because the lower price makes them more affordable for families. If that bothers you, look at the floor plans and pick a room away from the rooms that have the 1 and 2 upper bunks. Families often get these and have their kids in their room with them or put older kids in their own room.
In the older ships the higher the deck, the closer you were to everything. The newer ships put a couple of public decks lower. The Valor and Victory have the dinning and show rooms below the balcony decks. Being higher on the ship doesn't aways get you closer to the action now.
If you like to hit the beds early, you might try to get on a deck between two other cabin decks so you don't pick up noise from the public areas.
I guess is sounds like I'm obsessed with noise in the cabin, but about the only thing we do their is sleep so that's about the only real concern I have. The rooms are all big enough for the two of us and the views are all good. So sound and motion are about the only concerns. Other than that pick a cabin close to where you want to spend most of your time.