We've been to both repeatedly. I feel safer in Montego Bay port but that may be just me. Lots of fun excursions at both. Main advice is don't do excursions that go to the other port - too much time on bus and more dangerous. Say in Montego - don't go to falls in Ochos Rios... Debbie
If you want to do Dunn's River Falls, you're best bet is to take a cruise that goes to Ocho Rios & do the Cool Runnings excursion. It is a lot of fun! If you go to Montego Bay, it is an unpleasant bus ride to Dunns River. Make sure you wear substantial footwear for climbing the falls. Have fun!