Well, I had a chance to direct compare them side by side. The HE560 does feel noticeably lighter on my head due to their suspension design and weight distribution. The HE560 earpads are deeper and gives my ears more clearance.
The Oppo PM1's comfort was fine, but I did notice my ears brushed up against the driver like the above poster was complaining about. The PM1 does feel heavier on your head in comparison, but its weight is fine.
From my direct comparisons, I'd say the HE560 edges out the pm1s in comfort. You can feel free to disagree, but that was my personal experience after using both for long listening sessions over a fee weeks.
I completely agree with you.
For a wider range of comparison, I bring in the Ultrasone 8 as well, which is closer in shape, size and weight to the Oppo PM-1 than the HE-560. I own all three of these headphones.
The Ultrasone is the lightest and smallest of the group and comes closest to being considered "portable." The earcup and earpads, however, are not big enough to go over the ear completely. I definitely feel the pressure and the pain of the ear-pads on the ear lobes after more than half an hour or so of use.
Though heavier, the Oppo PM-1 have big enough ear-pads to go around the ear lobes "almost" completely. The operating word here is almost. The ear-pad openings are not big enough for my ears so they sort of squeeze the earl lobes a little to keep them inside the holes. I definitely feel the discomfort caused by the ear-pads larger pressure (due to larger weight) on the ear lobes after prolonged use.
The HE-560 is big and heavy enough to disqualify it from being a portable headphone for me--this is only my opinion, not a general statement; others may find them just fine as portable pair of headphones. The opening of the HE-560 are big enough to go around my ears ( true circumaural) without pinching any part of the earlobes. For short-term listening, I find the HE-560 very comfortable. For more than an hour or so, the weight of the the HE-560 becomes too much for me for comfort--the weight is much less that that of its preceding siblings, I grant you, but the HE-560 is still a pretty heavy headphone compared to the Oppo PM-1 and Ultrasone 8.
So for comfort for extended listening my personal preference is HE-560 > Oppo PM-1 > Ultrasone 8.