I have only gone on RCCL but from everyone I spoke to who went on both RCCL and Carnival, they always preferred RCCL. There is one dealbreaker for me. I go on the cheap, short cruises and RCCL goes to CoCo Cay while Carnival goes to Freeport. CoCo Cay is way better.
Looking for our next cruise!
Sovereign of the Seas (Sept 2002)
Enchantment of the Seas (Sept 2003)
Monarch of the Seas (August 2009)
Monarch of the Seas (April 2011)
Enchantment of the Seas- Port Canaveral (May 2013)
Enchantment of the Seas - (April 2014)
Hope for a BIG ship in 2015! (heck with that, we'll take a small one for 2014!)