We recently returned from the New Years cruise on the Mariner of the Seas, traveling with 10 family members ages 11 - 86. We had a great time. It seems that a lot people are looking for comparisons between the Mariner and Carnival Magic. Having sailed on both in the last year, here is my opinion.
We stayed at Moody Gardens the night before. For $20, they provide covered parking and very prompt shuttle service to and from the pier.
5 trips on Royal Caribbean gives me Platinum status so off we went to a very short line to get on the ship. Probably took us about 20 minutes until we were on the boat. Carnival takes at least 10 trips to get special line status.
Our balcony cabin on the Mariner seemed a little smaller, especially the bathroom. The shower doors were a definite upgrade over the Magic shower curtain, although at about 2.5' wide (circular) some guests might have trouble fitting. Both cabins were over seen by excellent cabin stewards.
Shows: On the first (welcome aboard overview) and last night (comedian and magician) there was only one show time and we missed them due to our dinner time. 2 nights had production shows with very good singers but the shows were much more entertaining on the Magic (even, surprisingly, the 70's show and the passenger talent show). 1 night had a comedian that wasn't very funny. The second comedian had a late night show that was a little better than the first. One night there was a Beatles tribute band and another a Whitney Houston cover girl. Although, they were very good singers, there was no show, just them singing. There is an excellent ice skating show that is put on 4 different times. The last ice show is the only show for that evening. Unfortunately, there weren't many other entertainment choices if you don't care for the shows.
Other entertainment: Royal Caribbean excels in its night time games, especially The Quest, which is a lot of fun. There is also a Family Feud type game and Hot Seat. Unfortunately, karaoke was only held 3 times, in a bar that is way to small. They also need to update their song selection. The piano bar was popular although that song selection could also use some updating. There are more live musicians (piano player with violins, Country Western band, mariachi band, jazz band) on the Marina but that isn't really something my family goes for. Caribbean sounding music by the pool on the Mariner was much more enjoyable than very loud current (sometimes Rap music) on the Magic. The casino was great, especially since I won $225 playing a $ .20 slot machine! I wish the entire area was nonsmoking though.
Dining room: One thing I really liked on the Mariner is their my time dining. You can make reservations ahead of time. We reserved a table for 10 at 6:15 every night and had the same waiters. On Carnival, there are no reservations for my time dining. This wasn't really a problem for 4 people. We rarely waited more than a few minutes to eat around 7 PM but didn't have the same waiters. We seem to get better service when the waiters get to know you and what you like.
Food: Although the Mariner had some great sounding entrees, in reality many weren't that great. The steak offered each night was very tough. Every night on the Mariner, we got a large plate of 2 - 3 different vegetables to share which was terrific. Overall, I thought the Magic had slightly better food, especially dessert, but the vegetables were mostly of the barely steamed type.
Crowds: The Mariner is broken up more so didn't seem as crowded where as the Magic has most of its entertainment on fewer decks. (The addition of entertainment and an outside deck on deck 5 of the Magic was a great improvement over the Conquest however.) The Mariner seemed a little cleaner as in not as many dirty dishes sitting around or empty glasses. The restrooms on the Magic are more crowded and could use a little more attention.
In short, mid 20's kids said definitely Magic wins, husband who doesn't really attend any entertainment said definitely Mariner wins, and me - I like them both for different things but probably give a slight edge to the Magic. I am the planner of the family and I like to work with the same Carnival vacation planner. Royal Caribbean wants you to use whoever answers the phone each time.
Ports: Roatan: Beautiful beaches, great snorkeling
Belize: Every thing in Belize is about a 45 drive after a 20 minute tender ride so we just walked around the shops, the kids got some internet time, and we got back on the boat. Does every cruise have to include one dud port (Progresso, Jamaica, Belize)?
Cozumel: Relaxing beach day while some went scuba diving.
One other thing, it was too cold to sun bathe on the first and last sea day. I've sailed out of Galveston in mid October and that was OK so that is probably as late in the year as I will go.