I just like being on the ship. To me, it doesn't matter where. If it's a special occasion, we'll get a balcony & did an aft balcony a couple of times.
As far as price, the higher you go, the more expensive it gets. On one deck, the middle is usually more than the ends.
Lastly, I try to pick a cabin that is surrounded on all sides by other cabins. You are less likely to have some odd noises from something like a janitor's closet early in the morning or a dance floor late at night.