I am not sure why you asked this question in the Mexico Thread since neither one is anywhere near Mexico.....
However, I have been to Labadee and it is a very, very nice port stop. The ship provides all the food and drinks so no worries about food issues or costs. The beaches are very nice and spotlessly clean with plently of activities available (most at extra $$). There are many stores ran by locals so you will have plenty of opportunities to buy local stuff if you want. The sales folks did not seem to be pushy to me.
Falmouth is a new port-of-call and I am not sure how long it has been open. The last thing that I read somewhere was that it is still a work in progress, but that maybe changing quickly.
05/89 NCL, Seaward, 1990 Carnival, Topicale, 1991 Carnival, Festivale, 11/93 Wind Star, Wind Song, 01/95 Celebrity, Horizon, 01/96 Celebrity, Century, 01/00 Celebrity, Zenith, 01/01 Princess, Ocean Princess, 01/02 Princess, Ocean Princess, 01/03 Celebrity, Summit, 05/04 Princess, Diamond, 01/05 Celebrity, Galaxy, 01/07 Oceania, Regatta, 01/08 RCCL, Voyager of the Seas, 02/09 RCCL, Voyager of the Seas, 01/10 Celebrity, Solstice