The most important thing to consider when purchasing headsets is whether they are comfortable on your head.
The heavier the headsets are the more that weight that must be distributed across your head.
Head pads are used to distribute the weight of the headset across the top of your head.
Head pads vary in design and range from ridged vinyl covered foam head pads to those that are covered with a thick, soft sheepskin over foam pads.
Ear seals vary in design from foam filled to liquid filled and their purpose is to distribute the clamping forces of the headset across your ears.
The speakers in the headset are responsible for the quality of the audio being reproduced in the headset and must have a good frequency response.
Look for an electret version of microphone with a good frequency response.
Microphones are mounted on a boom which is used to position the microphone in front of your mouth.
The boom is crucial because if not in the right place, the sound quality will not be as good as is needed.
Active Noise Reduction (ANR) involves the use of sophisticated electronics to cancel out loud, low frequency noise that is often present in aircraft, along with seals over the ears.
ANR headsets need power to function and will need to either be connected to battery packs or to an installed panel power module. Most battery packs last for 40 hours or more.
Passive noise reduction headsets depend on insulation in the ear cups and sealing over the ears to diffuse loud noises in the cockpit.