We took the shorter (4 hr.) Mayan ruins tour and really enjoyed the small group and great guide. He knows the historical significance, speaks English well, and he really showed us around the entire island. It was HOT! but umbrellas helped, and we stopped at a fabulous seaside-on-the-sand little snack stop and enjoyed the best ceviche and beers of the entire trip/cruise.
Low rating is because there wasn't enough time to do anything in port. Our kids bought a double ticket for Hemingway House and Truman compound but were only able to do one of the sights. My husband and I have been in Key West for an extended (and very pleasant) visit so we opted to go to bars (Hog's Breath and Margaritaville) and Harley shop. Very pleasant and un-rushed and catching shuttle back to port was no problem.