Haven't done either one of these excursions but you really need to book a tour before you arrive at the port. Hubby and I thought we would just walk around and shop, then book a tour, but much to our surprise there are about 20 tents and a rock quarry and no tours after about an hour that the ship docks. The prices in the tents are very high and they won't haggle with you. We really wish we would have done a shore tour. We spent about an hour on land and the rest of the day back on the ship. Good luck on your decision, looks like you will have a good time with either one.
Calica does't look like much, but you can take a taxi into Playa del Carmen, which is only about 5 miles north of Calica. Playa del Carmen is a beautiful town with a gorgeous beach. We love it there. There is also Xcarat nearby. Tulum is about 30 miles south of Calica, and is supposed to be beautiful.
Whatever you do, don't just stay on the ship. Get off and explore!!!