Oh, I agree, they both have their use cases. But that doesn’t mean there’s not plenty of situations where the performance is effectively irrelevant, but where people tend to default to using a hash map because they heard it’s faster (probably because lookups are O(1) indeed). So that’s where I would say, as long as performance doesn’t matter it’s better to default to B-Tree maps than to hash maps, because the chance of avoiding bugs is more valuable than immeasurable performance benefits (not to mention that for smaller data sets B-Tree maps can often outperform hash maps due to better cache locality, but again that’s hardly relevant since the data set is small anyway).