OTOH the list and struct types allow lots of complex operations, e.g with `.eval`, which run blazingly fast.

"Just works" is fine... Until it does not, and you have a hard time finding the issue. I prefer more control over my editor.

Std::set is using red black trees, did you mean std unordered set?

yes, the common complaint about separate chaining being effectively mandatory is about unordered_map and unordered_set. It looks like std::set suffers from essentially the same pathology though: you cannot use implementations with good data layouts (b-trees) because the standard imposes unreasonable requirements about iterator invalidation.

See https://stackoverflow.com/a/26552219