The use of type-aligned in freer extensible effects is aimed at minimizing the cost of "appends", i.e. monadic binds, when constructing (accumulating) a large pure free-monadic expression. This is avoided in a different way in the streaming libraries, which are also implemented as free monads. Something like freer will always be more expensive than the elementary transformers in transformers since it is a recursive type. The deep distinction is between recursive types like Free XYZ and stuff like StateT Int (and then again, under the latter heading, between recursive and non-recursive programs.). Because of the chance historical fact that no recursive transformer types are represented in transformers (I ignore the so-called ListT) it is possible to write infinitely many blog posts proving that transformers is better than free monads by e.g. comparing StateT with Free StateAction, which is permanently hopeless. But if tranformers had a real ListT we could e.g. compare ListT (State Int) Char with Free (Sum (Yield Char) (StateAction Int)) () or whatever, and the differences would not be particularly striking.