I think in reality it really comes down to what you like and enjoy on a cruise. For us it's the size of the ship (smaller for us), it's the restaurants on the ship, and we prefer causal dress, not formal.
We want a ship that has nice suites with a Butler--a cruise is time to relax and enjoy doing nothing. A show now and then, maybe some casino action, a cooking class and a private tour. It's your money, you should spend it as you see fit and what's right for you.