We have done Celebrity and P&O before. Enjoyed both of them.
We took two cabins as our 4 children were joining us. food was OK. Dubrovnik, Venice , Mykanos were good destinations, Sarande not worth getting off the boat for - dirty, full of beggars. Entertainment was comedically bad but became repetitive.Their musical version of Red Riding Hood consisted of lots of thrusting of sparkly codpieces.
Truly awful experience with an aggressive vibe from several members of staff while on board. Many ignorant, many rude, a few stood out as very pleasant. Many could not communicate in English. One member of staff explained they were so short staffed they would bring mechanical labourers from below decks to work as wine waiters in the restaurant. Shambolic