Having been to Belize 3 times and to Progresso once, I prefer Progresso.
It;s all according to what you are interested in. I love history and especially the history of the Mayan civilization.
From Progresso it's a couple hours to Chichen-Itza, a 6 square mile Mayan site that was just named as one of the wonders of the world.
There are several Mayan sites you can visit in Belize but nothing compares to Chiche-Itza.
However, if you're not interested in Mayan history and more into water sports, Belize would probably suit you better.
We will also be going to Playa Del Carmen on this trip for our second visit. They also have Mayan places there as well that are beautiful. I really enjoyed looking at the History of the Mayans. I'm a Photographer so I enjoy taking shots. As for water sports, I'm not really into it but do enjoy the beaches.
Playa del Carmen - tender port, excellent find sand beach right off the tender pier, but packed solid wall to wall people. Tons of souvenir-type shops, American fast-food restaurants , people coming up to try and sell you stuff. lots of water sports.
I call it a classic spring break beach.
Progresso - the beach near the 3 mile long pier is water with a fair bit of sediment, a fair to large amount of floating seweed. The surface in the water is often broken shells and stones, so it is a little hard on people with bad knees. In the late afternoon there were mostly Mexican families there, which I like. Not at all crowded at that time of the day. Far fewer restaurants and shops, and they are not as 'nice / developed' as the ones in Playa del Carmen.
I call it a classic beachcomber's beach.
Most beach seekers will prefer the beach at Playa del Carmen if they can stand the crowds and hawkers. Progresso is the best access to the major Mayan ruins. Progresso seems best known for city tours of Merida and trips to the ruins and not a whole lot else. I'd suggest you plan your shore days accordingly.
We took a river cruise last time in Belize which was quite interesting. It had the feel of being on the Amazon in the jungles of South America. Playa del Carmen is also a good stop and a jumping off place for XCaret.
Freedom Of The Seas -07
Radiance Of The Seas-07
Adventure Of The Seas-05
Navigator Of The Seas-04
Soverign Of The Seas-02
Big Red Boat-93