Having done STT for many years I am currently in the DCA/SJU/EIS camp....checking for our May trip DCA/SJU/EIS Jet Blue/Silver is currently $598 round trip booked together and DCA to STT is $412 round trip...and then need to add ferry both ways...
Also I find SJU has more last minute alternative options since we have been "stuck" in STT and Miami on the way home multiple times
From DCA there is rarely a direct flight option to STT and since we originate in DCA anyways I like this option better...
Didnt seem to me to be a shortage of options to either place but maybe I am missing something.
OP-That is a great handle...was just in my bilge yesterday putting heaters in