I second the motion. There is no ship to compare to the Freedom of the Seas. The "Voyager" class ships are the biggest ships on the seas. Never cruising before, you have no way to make a comparison to any other ship or cruise line. Any cruise line or ship will be a great vacation. Your question is which is the best ship, the answer is the FREEDOM OF THE SEAS.
Yes, the Mariner is a Voyager class ship. It was the last Voyager class ship built. The freedom is a Voyager class ship also, but it's an ultra or super class. Unless they changed the class to Freedom. There are going to be 2 more ships build the same size as the Freedom. The next class is going to be the Genisis Class in 2009.
Any RCCL ship will be great. As Sonny and Dave have stated the Voyager class ships have a lot to offer. Explorer is a Voyager Class ship. If you are going to Bermuda you'll want to have a ship with lots of onboard activities because of your time at sea. If its in the budget I recommend a balcony cabin for Bermuda. If not just spend lots of time on deck its all good because guess what?... you are on a cruise.