I've noticed a difference in earbud 'phones comfort as well. So, prodded by your post, I took out my micrometer and took some measurements on what I had laying around.
My favorite for sound has probably been the Sony (I think MDR-E828LP) and they feel fine for me. I've always had pain when fitted with the $1 earbuds from Walmart. What is interesting is that the Sony's are .66 inches acrosswhile the $1's are .65 inches. The difference is in the thickness of the--for lack of a better word--bezel (the thickness of the portion that is inserted and makes contact with the listener's ear). Sony's bezel is only .13 inches while the $1's are .17 inches thick. I think this is the difference for me in comfortable vs. painful.
The Sony's mentioned in the prior post (MDR-EX71SL and the similar-looking MDR-EX70LP) look identical to my Philips SHE9501 (which is white and has a black cousin with a slightly different number). These 'phones are inserted slightly into the ear canal, and can be fitted with one of three sizes of inserts. The medium are .42 inches across while the small are .37 inches. they are designed to flex within the ear, and when flexed are smaller (the medium "flexes" down to .28 inches, for example).
One thing I like about the Philips (which based on the picture looks the same for the Sony) is the short cord with removable extension cord. Though it's long enough for (my) shirt pocket to ear, it's a little shy for (a number of my) pants pockets to ear. Overall it makes a great, short, length of cord which reduces the tangling when stored in pockets.
Hope this geeky monologue helps.
Greg Smith
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