Have been on both the Valor and the Liberty....both are beautiful ships. You will however get lots of opinions from lots of different people as to what they liked best.
So, here is mine;
I liked the idea of the big screen on the Liberty to sit out and watch the evening movies, and the ship was of course beautiful. I however would never go back to Jamaica (Ocho Rios)....I pick my cruises based on the fact that that port is not in my itinerary.
You can still cruise the Liberty with an itinerary to avoid Jamaica. We cruised the western carribbean last year, and Jamaica was not in the itinerary.
The Valor was also beautiful, loved the decor on that ship as well. I will have to say that the itinerary on the Valor (Exotic Western) has been our favorite cruise thus far. In Belize we did a private cave tubing excursion that was amazing...much better than offered through Carnival. We definately plan on going back to Roatan again soon., we took a taxi to West Bay Beach in Roatan that turned out to be the most beautiful beach we have ever been to!!
As mentioned you will get many personal opinions on these ships and ports. Your best bet would be to read the reviews on each of the ships., and try and find some threads that have info on each of the ports of both ships.
We pick our cruises with the itinerary in mind.
hope this helps!