Need cash when I land, best place in Saint Barthelemy? Airport or places in the city?
My advice is to skip the exchange counter altogether. Most cards work at the ATMs, and you'll get a much better exchange rate than you will from any exchange booth. The ATMs are plentiful in Gustavia, so you can find a bank easily. I used my Revolut card at a bank ATM, and the rate was perfect. Just withdraw what you need for the day and then use your card for larger purchases.
The currency on the island is the Euro, so if you have that, you won't need to exchange money at all. If you're coming from somewhere else, you should absolutely avoid the airport exchange counters. Their rates are a total rip-off. My advice is to find an ATM in Gustavia. You can get Euros right away, and you'll get the real exchange rate, which is always better than what any currency exchange center will offer.
I've been to St. Barts many times, and the best way to get cash is to just use an ATM. Don't waste your time with the airport exchange booths. They have terrible rates and high fees. Just grab a taxi from the airport to your hotel and then find a bank. I've used the ATM outside the Credit Agricole branch in Gustavia, and it's always been reliable. Since the Euro is the currency, it makes everything so much easier.
Forget the airport currency exchange. It's a total rip-off. The best way to get cash is to use an ATM in the city. The official currency is the Euro, and there are plenty of ATMs available in Gustavia. You'll find them at banks like BNP Paribas and Banque des Antilles Françaises. You will get a much better exchange rate from an ATM than you will from any currency exchange counter, so it's not even a contest.