If you talk while you write or type or use tools or read or walk or drive or care for a child, you should have a headset. Many cordless and cellphones and some corded phones are equipped with 2.5mm jacks for headsets, and don't need a switchbox. Some cellphones need a small clip-on adapter.
Most headsets are comfortable for eyeglass-wearers.
A binaural headset will minimize the ambient noise that you hear. A noise-canceling microphone will minimize the ambient noise that the other person hears coming from your phone. Headsets with longer microphone booms will make your voice sound stronger, with less echo and less background noise, than headsets with short booms. Headsets with short microphone booms can be stored in a pocket or pocketbook, and are good for a quiet environment. Headsets with long mic booms make your voice seem louder, with less echo and background noise.