If your office is quiet, or you need to be able to hear people around you while on a conversation then a monaural single earpiece is a smart choice. Generally less expensive than the 2 ear models and can be worn on either ear.
If you are in a very noisy office or call-centre then you would probably benefit from a binaural headset as the dual ear pieces will keep outside noise out enabling you to concentrate more fully on the person you are talking to.
