You are so right about variables between ships. We were on Reflection in October and described the experience as "beige", not horrible but nothing to excite us which us what we are looking for when on holiday. A truly mass market experience to be sure.
Even Azamara offers a different vibe depending upon itinerary, cruise director and senior staff.
One thing that remains consistent though is friendliness and service from the entire ship. There are always lots of smiles and they can't do enough for you...something that is desperately lacking on Celebrity and other larger ships.