The best croissant in France is probably in the bakery of a tiny village in the depths of France, which a grandma has been preparing every day for 30 years. So I won't stress myself out too much by basing the choice of travel on this criterion. In any case, whether you go to Paris, Lyon, Marseille, Montpellier or St Malo, as long as you refrain from buying industrial ones from supermarkets or in the immediate vicinity of major tourist sites, you will have excellent tasting moments everywhere 😉