On cards that offer a free checked bag, most offer it only on domestic flights...which excludes SXM.

Regarding the Chase Sapphire Reserve, it's complicated, but a great deal if you travel frequently. You'll have to read up on the deals. The annual fee is $450, but the benefits are awesome. In the first six months I had the card, wife and I flew to Paris for free on the signing bonus points, got $600 back in travel credits (just taken right off the bill), got a discounted luxury hotel in Paris, and used a bunch of airline lounges for free.