I have sailed on royal once, but I loved the Liberty OTS so much that I have booked it again and have also booked a cruise on the Oasis. I have sailed on Carnival twice but don't plant to do so again.
Carnival Liberty New Year's Eve 2007
Liberty of the Seas 5/2008+11/2009
Allure 1/16/ 2011
Independence of the Seas 12/29/2013 Top-notch!