Benefits of promises. Lwt_io.printl and print_endline

Hey, is there any benefit in using Lwt_io.printl instead of print_endline ? I would expect there would be some tangible benefit when writing to a file since the IO operations on disk might be taking a while. Following the same logic, I would expect the Lwt_io.printl to be beneficial in a situation when I print a lot to stdout.