All ships are equal in customer service imho.
I think
DCL sets high standards and normally 99% of CMs are very very good.
I would say there is a slight difference in Cruise directors, some excellent like Christian and some more managerial and less touchy feely.
To consider booking I would say whittle it down by.
- The Month when you want to cruise.
- Where the ships are at that time.
- The ports of call you want to go to.
- If you do not mind crowds then the bigger newer ships are good, if you prefer less crowds the older ships.
For example, I have sailed most on the Magic that's as (1) it comes to Europe (20 has more interesting schedules. I haven't sailed the Dream that's because it does short 3/4 day trips, and goes to Nassau. I do not think Dream is a bad ship i just do not like short cruises and Nassau.
I didn't go on the Wonder for a long time due to that reason but went on it in Alaska for Alaska not customer service.