Which should I get a FAA glider licence or a Canadian glider licence?
This is heavily dependent on the local jurisdictions you plan to operate in and what their laws are. 

First off you must find out if your desired countries of operation accept foreign certificates. This varies heavily all over the world and can range from full no questions asked acceptance, to you needing to simply take the test again (in that country) through any various case you can think of. 

Second you need to find out what certificate you need. Here in the US to give rides (and receive compensation for such) you need a commercial certificate. This looks like it extends to gliders as well. 

Hours. 

The FAA requires a few more hours than the Canadian certificate will, 

FAA


  
  Are at least 16 years of age; and 
  Have logged at least 10 hours of
  flight time in a glider and that flight time must include at least 20
  total glider flights, and 
  Have 2 hours of solo flight time in a
  glider, and 
  Have passed the FAA written examination; and 
  Have passed the flight exam with a FAA Examiner.
  


Canada 


  
  A minimum of 6 hours of flight training under the direction and supervision of an instructor
  At least 2 hours of solo flight time, including a minimum of 20 takeoffs and 20 landings
  


Right off the bad Canada requires 4 less hours which, no matter how you spin it will be cheaper (since you have to pay for less time). 

Here is the US if you are not a citizen you will need to pass an NTSB background check to train. I do not know if Canada has a similar requirement. 

Travel, assuming you are in the Caribbean already it may be cheaper to travel to Florida (or the like) to train then go all the way up to Canada for your training.

Edit: 

According to this document the ECCAA does issue glider ratings 


  2.1.2.3 RATINGS ISSUED 
  
  (a) The Authority may issue the following ratings for pilots
  (i) Category ratings in the following aircraft:
  
  
  (a) Aeroplane;
  (b) Rotorcraft; 
  (c) Glider; 
  (d) Lighter-than-air; 
  (e) Power lift.