A slogan is a short statement that accompanies a brand over the long term and sums up its stance or promise. A claim tends to be tied to a specific campaign or product and changes more often. A good slogan is understandable without explanation, is grounded in positioning, and can be said without embarrassment even in a business conversation. The risk lies in claims a company cannot substantiate – superlatives such as "the best" or "number one" are subject to rules on misleading advertising and must be provable. It's also worth checking whether a similar phrase is already used by another brand and whether it can be protected as a trademark. In practice, a slogan alone doesn't build a brand: it only works once it's backed up by the customer's actual experience with the service.
See also: Trademark in advertising, Brand story, Unfair commercial practices.