You can't work a headset microphone.. That's why I've always avoided them. You can get a wide variety of tones from your voice by moving in close and going soft, or moving back and going hard, and all shades in between.

But that headset mike is going to be at the same distance all the way through the song, unless you are messing with it.

Plus, how do you deal with a cough while you are playing? Or an aside to a customer?