I am the happy user of a headset mic. In my opinion it has many more advantages than limitations.

Sometimes, when I'm singing louder, I reach up and pull the mic away from my face, and sometimes I pull it closer. So you can do that a little bit, but a hand held is probably better if these techniques are essential for you.

I like being able to look at every one in the audience, even people behind me as I sing and play the keyboard. I like not having to deal with a boom. I recommend that you purchase a headset mic, and return it if it doesn't suit you. One problem I had with a professional headset mic is that it wasn't loud enough. I turned the volume up on my PSR 740 all the way, and it was just barely loud enough. Instead of going with a mic preamp and complicating my life, I've been using a Radioshack headset mic for $49.95. I've been happy with the sound, and for $15 I purchased a 3 year warranty. I own two of these mics, and whenever one gives me a problem (every 6 months) I drop it off at the Radioshack and use the other one. I play at retirement homes, nursing homes, and schools. If I were trying to sign with a major record label, I would go another way, but the system I have works perfect for me. Good luck!