NCL is not my favorite line as the staff don't seem to care much and the food edible of course but not impressive. Celebrity in on another level in those regards. I did spend 3 weeks on the NCL Epic so it's all about making the best of things; the ports were great, the weather was gorgeous, the ship has lots of things to do like the breakaway.
How did you like your NCL trip vs the Celebrity experience? If you enjoyed both equally then don't worry. Personally if both lines are going where I want it's not a choice for me but if NCL goes somewhere Celebrity doesn't I would consider it.