I have a boat in Jolly Harbour (I will be there tomorrow).
Moorings in Jolly Harbour-I don't know what they cost, a stern-to slip would probably cost you about $500, but call them up and ask. Only problem with mooring in JH is the powerboaters who storm in at 20 knots and kick up a wake. The marina has no "no wake" buoys and they won't let me install any at my own cost, I have them sitting in the boat house.
JH is in my opinion more convenient for provisioning and hanging out, much less snobby than Falmouth/English Harbour, and closer to the main town (St. John) but there are more sailboat services in English/Falmouth Harbor. I mean in JH they can paint the bottom,change your oil but there is no sailmaker in JH. All the marine electric, refrigeration etc. people work out of the English Harbour area. They don't like to come to JH and the last time (Antigua Sails) did work for me, they also agreed to change the bulb in my tricolor, and reinstalled it backwards. I cannot get them to come out to fix it.
If you just need someone to tend the boat, make sure it does not sink, I would go for Jolly Harbour, but if you want work done on it English/Falmouth.