You all probably know this but don't forget that your perception of the rocking motion of the ship is minimized by moving more toward the center of the ship, not necessarily the deck. It does stand to reason that an upper deck midships cabin will move more in pitching seas than one several decks directly below. But these spaces will likely move less than cabins toward the bow and stern.
We were on a RCCL cruise for our honeymoon many years ago and we picked the cabin from a brochure that had deck plans in it. Seems the cabin we picked was double the size of other cabins in the same category (lots of floor space), but way at the front of the ship. On our return leg (7 day Bermuda from NYC), we sailed through a cold front that had caused pretty big waves. The last day, I woke up, tried to start my day, but wound up going back to bed. Watched my wife pack. Never left bed until right before dinner which I still couldn't eat.
From that day we decided that mid-ships cabins were probably the best bet regardless of the deck. Outside cabins always! Balconies only if we feel expansive.