We sail both Celebrity and Princess. Our last Celebrity cruise was in January on Ascent. Probably one of the best cruises we’ve ever had. So, I would choose Celebrity over Princess, depending on itinerary.
I don’t know if it matters to you, but on Princess smoking is allowed in the casino and it tends to waft out into the surrounding areas. Of course, Celebrity has been indoor smoke free for years.
Sun Princess is not a ship I would be interested in, personally, so I can’t help you there.
Good luck with whichever ship you choose.