Well - it looks like I'm a minority here - I strongly prefer the comfort of headsets over helmets. Fortunately, my present position affords me that option.
For much of my career I've certainly worn helmets. I would never argue that headsets provide as much protection; indeed I'm aware of lives saved through the use of Kevlar helmets. However; many of us who fly SPIFR prefer to wear a headset. Why? It doesn't limit our periferal (sp?) vision in the cockpit.
Finally, I'm acquainted with a taller pilot whose head hits the overhead console of his aircraft when wearing a helmet - probably not the best situation. For this reason, he prefers the use of headsets.