The sound is different, but the comfort is night and day. These put all the pressure on your head vs your ears. Whats crazy is the pads fit directly on without any mods.
Edit: The headband pad is from a ruined 555. It works for the time being. I'm looking to get one custom made hopefully this weekend.
Thanks for the suggestion. I have an older, spare set of HD-555 pads that I removed from my HD-555 when I ordered a new set from Sennheiser. It might be worth pulling them out and checking the comfort option.