Best Guesses For "Best" Claims

If you want to advertise that something is the "best," do you need substantiation? Or can you rely on a puffery argument? Although the answer depends on context, one paragraph in a recent NAD decision seems to conflict with longstanding precedent.

NAD has frequently held that whether a superlative like "best" requires substantiation depends on whether the superlative is linked to attributes that can be measured. For example, in a case involving NyQuil's "best sleep" claims, NAD stated that "although claims of general superiority may constitute puffery, NAD has consistently concluded that linking a general claim to a specific product attribute may result in the need for substantiation."