Most of the film is set in New York, on the Larrabee's Long Island estate and then in the big, bad city where Linus works. But the movie moves to Paris when Sabrina goes there for cooking school.
Paris may not be in the film much, but it's hugely important—both as the place where Sabrina turns from caterpillar to butterfly and as a place that is portrayed as the opposite of The Big Apple.
New York is presented as a place of practicality and business; David has his fun there, but it's really the domain of Linus, bankers, and business deals.
Paris, on the other hand, is:
SABRINA: […] for changing your outlook. For throwing open the window and letting in… letting in la vie en rose.
Paris is a land of fantasy, mystery, and magic. In this Cinderella story, Paris has a role as a fairy godmother.
Is New York really 100% bland and boring? Is Paris really 100% mystical and awesome? Of course not; Paris can be dull, and New York has its share of infamous nightspots—in fact, Sabrina and Linus go to a lot of them. And the opening of the movie, with its "Once upon a time" voiceover presents the Larrabees' Long Island estate as a kind of fairyland.