Warning: I am not a leader and I haven't been dancing very long, so this is purely opinion, based on idle observation and not a deep understanding of technique.
When I first saw the video of Tim Ferriss setting the Guinness world record for number of giros in a minute (frequently labeled "world record in tango" which seems silly to me), I kept thinking that can't be very much fun. All I had to go on was my experience of how giros feel to perform. Watching Alicia Monti race around Ferriss just didn't seem elegant or graceful - just racing. The video can be found here (feel free to skip to 4:00mn so you don't have to watch the silliness that precedes it.
Then last weekend I watched our guest teachers, Oliver Kolker and Silvina Valz perform a beautiful milonga at Esquina Tango. While I was reviewing the video (which is a little dark, unfortunately) I watched Oliver's feet executing his very fast giros. His steps, in comparison to Ferriss's, are fluid, musical and graceful - complementing Silvina's steps beautifully. The video is here:
Granted, Oliver isn't trying to set a record for number of turns - so efficiency is not his goal. But still, the difference, to my untrained eye, is striking.