Ok, I guess I am one of the people who can really submit a little bit more balanced of an OPINION...if that is possible, as I have both the HD 580 and the ER-4s and I have good amps and sources for them. Personally, I reach for my 580s more often than my Ety's. Perhaps this is more telling in itself than anything else I will say. I really do love my Ety's, but I find, as TimD did that I don't use them quite as much. Personally, I agree almost completely with MacDEF (as I almost always do...) -- When properly powered, the sennheiser sound appeals to me a bit more. It requires less effort to listen to. The Ety's are very very detailed, and you will hear every single pop, hiss, and space between each note -- this is often a very good thing, but try listening to a cycle of Bartok's string quartets like this...it can be a little much. I find the sennheisers more comfortable in their sound as well as in their actual fit. They are like soft ear muffs, yet I do not really get hot in them. As for the Ety's, I can go for about 1.5 hours with them comfortably, after that I start to think about them, and this is with the foam, not the white-tips, which are generally regarded as less comfortable, but perhaps better sounding. One problem with the Ety's, if you are concerned about usability, is they don't just slip on and off like the 580s/600s, it is possible, but if you are going to have to take them in and out every 15 minutes to talk to your roomate or something, I guarantee you are going to get annoyed. Also, the cable is very microphonic, and it can also be a pain in the ass if your favorite seat is more than 2 feet from your stereo, as the cable is only 5 feet long. But for drowning out that annoying guy upstairs or nextdoor, the ety's are unbeatable. They are also great on any of the incarnations of the MTA. Libraries and cafes too benefit from their isolation. As for durability and upkeep, I think both are fine. I had the 580s for three years, and then the cable messed up, so I upgraded to clou cables, and have been very very happy. Otherwise they seem pretty durable...I have brought them around in a backpack to many places, haphazardly toss them onto beds and furnature, and I have missed and hit the floor more than once with no (well, no grattle anymore...) real damage. Ety's are physically pretty solid as well, and as utdeep said, they have less mass, so physical punishment will probably do less damage...Ety's can be a little bit more of a problem depending on what type of user you are. If you are fine with the white tips, then you probably will have little upkeep, as I think they last a good while. The foamies tend to deteriorate a little more quickly, but I have had the same foamies on for about a month, and I suspect I will change them in another two weeks or so. I really appreciate the niche that both fill, but unlike utdeep, if I had to choose between them (god-forbid), I would go with the 580s. Perhaps I am in the minority. But coming home and just slipping on those cushy velour padded monstrosities and falling asleep to some beautiful relaxing music is not something I would risk doing in Ety's, and it is one of the aspects of listening I like the most.
Woo, that's done. Good luck making a choice.
Stuart