Performance (execution, memory) is generally in the same ballpark as the BSD versions, with some caveats specific to utils that do lots of in place data manipulation.

cut comes to mind as an example, slicing and dicing lines into fields quickly without a ton of copies isn't easy. Using Streaming.ByteString generally makes a huge difference, but it's extremely difficult to use unless you get can your mind to meld with the types it wants. Picking it up again months later takes some serious effort.