This past May I flew to St Thomas, connected on Cape Air to St Croix. I'm a plat, I was off the aircraft and to baggage claim in aboout 12 minutes, waited about 3 for the bags. Walked over to Cape Air counter, checked in, went to gate 11 and waited for the flight. There is no security for Cape Air flights. The whole process from landing to being at the Cape Air gate took about 30 minutes.

In regards to Seaboure vs Cape Air. I would say it all depends on your desitation on the island. If you're getting a car then it doesn't matter. Seabourne does have float planes and gives you different options for destinations.