We have used IC 4x with no issues...flown Seaborne/Silver, Cape Air and private charter. You can search this site and find pros/cons of each. I am in the DCA/SJU/EIS camp and avoid the STT/ferry option...

On way out we do have a long layover at SJU with EIS. There is a later flight but dont want to miss the SJU/DCA connection. We also find easier to find options to states from SJU than STT

IC is the cheapest...