For some reason, AC/DC's "Hells Bells" makes the 4.A shine. I guess it comes from a combination of dynamic range (from low-pitched bells and drums to high-pitched electric guitars) and spatialization (the instruments' placement is so precise as to open the headstage).
Two days ago, I had the occasion to try a good number of headphones and earphones. As I'm usually a "grass is greener on the other side" kind of guy, I was surprised (and my wallet relieved) when the 4.A ended being my favorite, though it didn't win in every category. It lost to open headphones on airiness (compared to the HD 800, it even sounded congested) and to some dynamic earphones on bass weight. On the other hand, it constantly won on balance and timbre. What surprised me most is that, while a few headphones seemed to have greater clarity than the A.4 (again, the HD 800 comes to mind), the A.4 at least equaled them in actual detail retrieval. Of course, in the noisy environment of a store, open headphones were at a disadvantage.
And of course, the A.4 being my favorite doesn't mean it would be yours. The aforementioned HD 800 is a wonderful pair of headphones, but I felt it become fatiguing in a matter of minutes. Someone less sensitive to highs would enjoy them more.