Ron,
The CM-311A is what I have been using for the past three years and while it is not the most comfortable headset mic, it DOES provide the best overall sound quality of any headset mic I've tried.
I have used the Audio Technica PRO8-Hex, which is OK at best, the Countryman E6, which was very thin and best suited for lecturers, Samson (can't remember the model number) and Shure, which was almost as good as the Crown.
As for using a headset mic versus using a handheld, it takes a bit of practice to develop the vocal control required, but once this has been achieved there is no turning back to a handheld. The freedom a headset mic offers is one of the biggest attributes. You no longer have to worry about where the mic is while performing other tasks on the keyboard, or just changing your seating position.
You can easily maintain eye contact with the audience at all times while singing and never worry again about inadvertent bumps against the mic stand or body.
The mic has a cough button, which can be set for either momentary use, or as an on/off button, and there is no popping sound when the button is pushed for either operation.
Some singers like to utilize a pull-away technique, particularly when trying to hit the highest notes. Obviously, this is not possible with a headset mic. However, if you don't have to strain to hit the highs the headset mics, IMO, are the best thing since peanut butter & jelly sandwiches.
Good Luck,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)