I've been on both and it would just be my preference, but I'd choose the Noordam. I went on the Millenium BEFORE her very recent rennovation, though, and it was a MESS! I do not like that Celebrity lets the ships get that beat up before a dry dock. However, since it's been spruced up recently, I'm sure it's lovely, though I have not seen it. I was on the Noordam less than a year ago for a 10-nighter and it was in immaculate shape and the service was excellent. I don't think you can go wrong either way, but since you've asked for opinions, mine is Noordam. Enjoy whatever you choose!