We have been in the Haven about 5-6 times and did the Celebrity Apex Retreat earlier this year. Bottom line, you can't go wrong with either and I would make decide based upon itinerary, price, etc. With that being said, here are some general observations:
1) The newer the ship the better the Haven. Smaller NCL ships do not have all the same benefits as their newer ships.
2) The Apex Retreat pool/sun lounging experience was vastly better because the Haven has an indoor pool without ocean views. Celebrity's new ships (Apex/Beyond/Edge) have beautiful pool decks
3) If you have a COURTYARD Haven room, you don't have to take an elevator to the Haven pool/restaurant/Lounge. We have always had a Courtyard suite on NCL. We were worried about needing to walk from our room to the suite area on Apex - but in the end, that didnt seem to be a big issue.
4) We found the dining room on Apex to be very loud. We prefer the dining areas In NCL when there is a Haven restaurant.
5) It seemed there were more 'little things' offered on NCL. Little treats in the rooms, Escort to seats, etc. Not deal breakers, but felt a little more special on NCL.
Food options and specialty restaurants were similar and awesome on both. Entertainment seems better on NCL. If you are looking for a relaxed suite experience, would lean Celebrity Retreat. If travelling with friends, looking for a party, would lean NCL. But again, they are both great!
