It depends on what you're looking for. I have been to both. 2002-shore excursion from Royal Caribbean to Tulum ruins with a stop at Xel-ha. You walk through pathways, lots of Iguanas everywhere, big ones but harmless. There is a large lagoon, I think they call them cenotes, looked like a big quarry with very clear water. You can rent snorkel equipment and floats here. There are stone steps leading down into the water. I think there was a dolphin area but that cost extra. We just explored the paths, one took us to a beach with tons of coral. There was a topless woman there, grandson(15) turned purple, didn't know where to look! There was an area with large parrots,also. One of them sat on his shoulder and ate the button off his baseball cap. We still laugh about that. I have a picture. 2003- shore excursion from Princess to Xcaret with daughter. I wanted to do this to float through the underground caves and we did this. They give you snorkel equipment and a vest and the water is very cold, but Mexico is very Hot so its ok
This is an eco-park, quite large, there are animals to see also. You can buy food there, and there is a large souvenier shop. Only thing I didn't like is they said they had no US money for change so I didn't get to buy what I wanted for gifts.
I enjoyed both of these parks for the experience, but would not try to go on my own, unless I was already on the mainland. If you are off a cruiseship docked in Cozumel, you need to take a long rough ferry over to Playa Del Carmen to access both these places, and from there is a bus ride, takes quite awhile. Hope this helps you make a choice. Xcaret is more expensive, if I recall. Both are fun.
We preferred Xcaret, but went to both Xcaret and Xel-ha on land vacations, not cruises. Xel-ha is very large and things are further apart. My feeling is that snorkelers seem to prefer Xel-ha, but that's not me. The "lazy river" at Xel-ha becomes a HUGE, wide river and it gets boring flapping your arms forever - it took up most of our time and I felt we didn't get our monies worth. The underground river at Xcaret is really cool - long but not too long, well-lit by natural light coming in through cenotes (holes in the ground) and openings where you can disembark if you feel like it. The walkways between attractions are shorter at Xcaret and I think that there's more to see. At Xcaret we did the quickie guided tour to get the lay of the land, and then back-tracked to the things that we were interested in.
Jean, I just skimmed through this subject again, and read your answer on cenotes. Thanks for the description, I wasn't sure, I thought it meant the lagoons and underground water. I enjoy learning something new every day, which is why I read these boards. They are so informative and we can really help each other.
My sister went to Xel-ha and loved it, I saw pictures and it's beautiful. Can't say about the other site I've never been to eather, good luck, have fun. Oh she did have to buy a special ecologically safe sunblock there though.