I've sailed on Millennium (in 2004) and on Dawn Princess in 2005 (not Sea Princess, but the same company and a slightly smaller ship); we've done Celebrity Summit and Galaxy also. We loved both, though of course Celebrity are designated a 'Premium' cruise company, whereas Princess only achieve 'Standard' in the Berlitz rankings - you should check out Berlitz for what the differences are, to see if they'd make a difference to your choice. Celebrity are better on the small touches - service is better, they use proper crockery (not plastic) in their self-service buffet and real linen tray mats, napkins, etc. Food is generally reputed to be better on Celebrity, though we found the self-service buffet much better in the evenings on Princess, with more choice - on Celebrity, all you can choose is stir-fry, pasta, pizza or sushi, which can be a bit dull. Staff are better trained and more professional on Celebrity and the overall cruise experience is classier.
Hi Ive been on the Sea princess twice. The first time it was our first ever cruise and it was wonderful. However, 6 years later we went again (came back 2 weeks ago - 16 Nov 08) The food and the entertainment were no where as good. Been on Celebrity Galaxy and although the ship was tired, the food was much better both in the buffet and the main restaurant. The best deals around seem to be on the Princess (particulary the Sea Princes) but you get what you pay for. The flight to Barbados on the Sea Princess was the worse flight ive ever been on in 33 years. Seats too narrow. okay if you way 8 stone, no good otherwise. I would say avoid Sea Princess. Cabins tiny also. Hope you find this helpful.
Simple Princess are a 4 star line. Celebrity are a 5 star line. Celebrity are regarded as the 'foodie' line & ports of call are subjective to your own needs & wants, only you know what appeals to you.......Wilba.