I've stayed in Oceanview cabins on both decks before. No issues being on those decks from my perspective. One positive is that on port days, if you're on deck 2 or 3 you can usually skip the elevator when coming back to the ship and just walk up the stairs. Very helpful when there's a crush of people coming back at the same time as you.
There are a few Oceanview cabins on Deck 3 that have a larger porthole window than the rest. Cabins 3115-3127 on the port side & 3112-3144 on the starboard side. These rooms were once public space that was converted to cabins, which is why they have the larger windows.