I think depending upon the type of detector you have also plays a part in how comfortable hunting with our without headphones can be. I find the Garrett detectors I own are not too bad to use with no phones, but my Explorer XS, I hate hunting with if I forgot the headphones or the ones I have decided not to work properly that day.
With that said, I prefer the phones, especially since the vast majority of my hunting is in Fall, Winter and early Spring. Ocean beach hunting, headphones are an absolute must.
I use Gray Ghosts NDT's and fine them super comfortable, and great tone for Explorer's. The only downside to them is they block outside noise so much, that when I hunt with my son, I cannot hear him yell or talk to me while we are hunting together, so I usually put one earpiece off my ear to hear the outside sounds......
A little side note, although I am a strict believer in using headphones, as far as statements about missing alot not using them, that all depends on the person, more than the detector and headphones.
I have a friend who has published his colonial finds in the C4 (Colonial Coin Collectors Club) newsletter and he has found more Colonials and more buttons, and artifacts of Colonial era than 99.9% of us will ever find. Guess what, he hunts the fields of NJ with no headphones! Oh, his article is on one thousand colonial coins found by him in Southern New Jersey.
I hunted with him this year and sure enough he does not use headphones, but he knows his detector very well and again, that is a major factor in your finds.
As far as the original question in the first post, I woud think using earbuds would most likely be very nice to try in hot areas where the full sized headphones are way to warm to wear in the heat of the day.
Don