I have visited Lamanai and Xunantunich. On the Lamanai tour there is a
boat ride on the New River and a walk through the rain forest. On the
Xunantunich tour there is no boat ride and your walk to the ruins is
very short. There are more museum pieces to view at Xunantunich.
Do a search on these two Mayan sites and see which one appeals to you.