He's not arguing that crit-bit trees are better than hash tables, he's arguing that they are a better choice for the fundamental set datatype for languages like

He's not arguing that crit-bit trees are better than hash tables, he's arguing that they are a better choice for the fundamental set datatype for languages like python, perl etc etc. When you write an application, you know the performance requirements of the set representation you choose & can pick the most appropriate for your application. A language designer doesn't have this information: their choice of fundamental datatype affects everyone. Bernstein is arguing that they should choose a set representation with good performance for as wide a range of features as possible rather than one that performs well for a small set of requirements, and very poorly for others. I can see arguments both ways here, but FAIL is a bit too strong IMO.