I think it depends on your goal. If you are training for fat loss, the fact that you're in a fasted state means your insulin levels are low and that that can lead to the body using fat to fuel the workout. The workout itself should be short and intense as well. This will elevate your metabolism all day. The Tabata Protocol lends itself very well to a fasted training session.
If you're training for muscle mass, size or strength, a protein shake with some good low glycemic carbs 30-45 minutes before training is a good way to go.
Make sure to refuel proper after training as well regardless if which direction you go.
Let me know if that helps.