You might want to take a look at shore excursions and see what you can do in each port, as well as research the ports on line or at your local library. Read reader ship reviews for both ships pn this site. Carnival will have more children on board compared to Celebrity if school is not in session, singing, dancing waitstaff, r rated comedy shows, and lots of activitys. Food will probally be better then RCL but not as good as Celebrity perhaps, also more casual dressers not as formal overall, but fun active ships with outgoing staff. I cruised on the Legend the Pride's sister ship and my cruise was wonderful. Im now booked on the Pride this fall. Happy cruising!
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Carnival Mardi Gras 1987 (Bahamas)
Carnival Legend 2005 (Exotic Western Caribbean)
Costa Mediterrenia 2005 (Eastern Caribbean)
Carnival Pride October 2006 (Mexican Rivera)
Carnival Legend 2007 (Western Caribbean)
Carnival Glory 2009 Western Caribbean
Carnival Liberty 2011 Eastern Caribbean
Norwegian Spirit 2011 Western Caribbean
Carnival Miracle 2012 Southern Caribbean