We were also just in an outside cabin on the Jewel, deck 5. It was fine -- and the inside ones looked basically the same layout. The only weird thing is the deck layout when it comes to getting to Tsar's palace (one of the main dining rooms). It's located deck 6 aft and you can't get there from deck 4 or deck 5 without going up to deck 7 at either midship or forward, walking aft on deck 7, and heading down a half-flight of stairs to the restaurant.
Also, the gangways for the ports are on deck 4. I don't know if that would lead to any extra noise, but you might want to be aware of that aspect too.