I've fished in both locations more than once. Belize has more flats fishing if that is what you are after. However, depending on where your cruise ship lands, it may require additional travel to get to a suitable location for flats fishing. In Coz, the flats fishing isn't as good as Belize or other locations around Ascension Bay... but still worth a try. A side trip can be easily arranged there. If you are interested in a guide, I can recommend one. Coz also offers deep water fishing.