Out of my experiences I would rank them:
1. Sennheiser HD570, lightweight with reaaaally soft pads. I think they would be the same as previously mentioned HD590. These are so far the only 'phones I have tried that I could wear all day without being bothered by them I think.
2. Sennheiser HD650, well stretched out pair with no clamping problems that I read about from time to time.
3. Grado SR325i, (chocker huh?
) somehow the store that had them on display had "squished" the bowl pads (by having them on the headphone hanger they had I think) so these were actually very comfy.
4. Alessandro MS1 w. 414 pads reverse modded.
5. Audio Technica ESW9, get´s a bit clampy on the ears after long listening sessions plus I wear glasses so I think that´s a contributing factor.
6. AKG K701, (other chocker
) I found these quite uncomfortable, the reason being partly that the headband didn´t stretch out far enough for my big head, so they were constantly sitting to high on the head. Plus they clamped a bit so my glasses got kind of pushed out and got all crooked.
7. AKG K518, yet another example of AKGs having a too small headband for me, couldn´t get these to fit on my head in any sensible way, the only option that worked "well" was having the headband going behind my neck, and that would not have worked when moving around.
That´s all I could remember at the moment.