Quick comparison: If you want me to go more in depth, I can. But I am going to be away from home for until mid-July. Also before I start I would like to say I would never buy the 580s. They improve a lot with HM5 pads and a sennheiser headband, and in my opinion are unusable without them.
Also, my Hp100s have dt770 pads on.
- They are both about as easy to drive.
- 580s have a much more engaging sound to me. Probably due to them being not as laid back as the Hp100s (if at all)
- Vocals sound more textured on hp100, just about everything sounds more textured and full actually.
- Soundstage depth seems about the same, maybe slight advantage to HP100s
- Micro details show more on the Hp100s. Some of the things I am hearing now I had to search for on the 580s
- Vocals sound thicker on HP100, although still somewhat thin to my ears.
- Bass impact seems similair (I didn't listen to a particularly bass heavy song- "Don't Lie" by Black Eyed Peas [320kpbs]) Hp100 trounces the 580 in sub bass, however.
- HP100s are laid back sounding, and more natural sounding
- Hp100 with velour pads is comfier than 580 with aforementioned upgrades. Mostly due to less clamping force.
Comparisons done with 320 kpbs songs playing from an iPhone 4>iphone dock>Schiit Magni>headphone
Also, I would suggest trying out a Bose AE2 before purchasing either of these. More natural sounding, more comfortable, and wider soundstage than either of these (Yes, even with the Hp100s amped, and AE2s coming straight out of an iPhone.
If you are looking to use these as porables, I would say look elsewhere. Both can easily be driven by an iPhone, but are very large. If I was being forced to use one portably, it would be the 580. (only with a 1m cable, mine has the 3m cable and it drives me insane)