I just got my old set of DT880 03 back, I just A/B tested them with my new DT880 2013 (I guess it's the 05 model) @600ohms and the sound is very different.
It's the first time I was earing my 03 on my Auditor and I must say, wow. First thing I noticed it's the bass difference, the 03 have way more bass, I mean not slightly more, they have plenty more. On some track I feel my 03 literally shake on my ears, while the new pair you barely ear the bass.
On the mid range I would say that the new pair win, it's more precise (maybe it's because the auditor prefer the 600ohms load vs the 250ohms of the 03). On the high range I don't see a huge difference, at least not to my ears.
So far I think the 03 will stay my best headphone so far. They are a bit more comfortable too (maybe because they are older). The cable on the 03 is more flexible and have a more "rubber" feeling, the new model it's more rigid, maybe because it's new..
Well, that's all, I guess my next buy will be the T1, waiting for an opportunity.