I find nearest the center to be the best, at either end, ship movement is slightly more prevalent. I have noticed in new ships the very expensive cabins have migrated from the aft to midship.
There's no definative answer as it's personal choice at the end of the day. Mine is as close to the rear stairs/lifts as possible to be in a vertical line to the eateries. Others will give a different veiw. Regards .
The cabins with a balcony looking out over the stern of the ship and those on the bit called "The Hump", that is the bulbous bit in the centre of the ship are always the first to be snapped up and by that token should be the cabins to go for. .... Neil.
Go for the centre of the ship the higher you go the more you feel the ship move.
First thing you need is a deck plan and a good agent? on all ships there are some cabins that offer bigger balconies or even more space than others as they are in odd corners that would not at first glance appeal you need to look above and below the cabin you fancy as you could end up under a deck where they move the furniture around at 6am or over the disco or sound stage.After that all the advice you already have is good,and on most ships the same food and facilities are yours to use whichever cabin your in?
I always go for an Aft balcony. Bigger balconies, no noise and great views.
I was always told to go to low deck, and then centre ship port/startboard , and then centre fore to aft. It usually means an inside cabin but for absolute peace and quiet it's heaven.
On Costa ? unless you particularly like Italian and French culture I would say none.