There's really many answears for your question.
Freedom of the Seas is a bigger ship than Mariner, but these two ships has mostly the same stuff to offer. The H20 waterzone, the bigger rock-climbing wall, boxing ring, and The FlowRider is the new activities you will find on board Freedom. The Freedom of the Seas is also able to board almost 1000 more passengers totally, than the Mariner Of The Seas.
There is many differences, and I will recommand you to watch some pictures from the Freedom Of The Seas, to see for yourself
Towards the bottom of this excellent review of the Freedom Of The Seas by Tom Ogg, you will find some photos of the H2O Zone.
We were on the inaugural cruise and both my son and I fell in love with the H2O Zone. You have a regular pool with a waterfall, the circular pool which has a counterclockwise current, some water spray guns, sprinklers, etc. It was really quite fun and it also served a valuable purpose - it kept most of the younger kids away from the main pools so they could be enjoyed by the adults.
Thanks, I hope to have a lot more of the Freedom after next week. Really looking forward to this cruise, it only got up to 34 degrees here today. I'm sick of winter already! We're leaving at 6:20 AM tomorrow.
I may just drop a note to you all from the Freedom...
I have not personally been on the Freedom yet. And I am not a person that thinks bigger maybe better. But from what I have read and that I have seen ( thanks to Sonny) Freedom has things to offer that others don't and that makes a difference. Now the catch is for me is does those differences mean anything to me? I do not surf so maybe catching a wave for myself is not that good, however, I do like watching others who enjoy it. In my past cruising experinces and I have post most/some of them on this website bigger only had bigger crowds. I am sure that the Freedom is awesome and I am sure Liberty will be also. But I loved the Mariner (just wished RCCL had given her more ports of call which could have been done) I loved the Radiance which I loved more than the Mariner because she visited more ports the thing is that cruising is for the people and you have to chose what you love about it and pick the experince you want after that. So just have fun on the one you chose for that moment is my advice. Hey Sonny great pictures of the SOS