My first BT headset was a Motorola HS850.  Worked well until the recharge plug snagged on the socket and parts of the socket came out with the power plug.  So I replaced it with the Plantronics 510.  I wanted an earpiece that inserted into my ear as oppose to laying on top of my ear like the old World War 2 headsets of 50 years ago.  I sometimes am in noisy environments and the "lay on the ear" type is not designed to isolate loud distracting noises.  The HS850 was difficult for me to hook over my ear and took both hands at times.  Not so with the Plantronics, at least for me.  It goes on my ear much easier and the earplug type earpiece shuts out more of the noisy world attempting to interrupt my communications.  The earplug type earpiece also provides vastly improved volume.  I had to crank up the MOT to full and still had trouble hearing it at times.  Remember, I'm not in an office cube with carpeting and noise absorbing fabric cubicle walls, but in my truck on the highway or on the plant floor.  The clarity of the sound is excellent.  The volume level is more than adequate for me with several levels left to crank up the volumn if I need to.