In name, they are each other's equal within the kingdom, but there is a 'slight' difference in size.

Also, 3 other islands in the Caribean are part of the Netherlands, the country: Bonaire, St Eustatius and Saba (but, if I have to believe Wikipedia, those 3 are not in the euro zone; the US dollar is legal tender in (part of) the country of the Netherlands)

(https://en.m.wikipedia.org/wiki/Kingdom_of_the_Netherlands)

The French have more overseas areas, and manage to make things complicated, too, with overseas departments, countries, territories, and collectives (https://en.wikipedia.org/wiki/Overseas_departments_and_terri...)

St Barts and St Martin are not overseas departments of France. They used to be part of the Guadeloupe overseas department, but seceded to be a "collectivite d'outremer" (overseas collectivity), which is different status than overseas department or overseas territory (France also has a few of those). St Barts (really "Saint Barthelemy") and St Martin not collect income tax locally and it goes to their budget (I think they wanted to stop shipping all their monies to the French state and/or Guadeloupe).