Well you know, I wasn't really paying attention to the model, only the brand, but when I listened to SONY MDR-7506, I looked at the model number and price, then tried the equally priced Sennheiser, and swapped it with SONY, then back, then to AKG, then to SONY, and back (so many times and also changed the music piece once or twice) and then I went home. After a week when I got the money, I bought it.
Sorry, I couldn't tell you about the AKG. Only the Sony that made an impression on me. Some of the headphones I heard made the music sound real good. Better than SONY actually, BUT - SONY was accurate. A little bright, perhaps, but that is because you could hear everything, just about. Oh, the detail it gives you, even how the drum stick hit and left and even slightly scratched the surface of the cymbals, perhaps. I was in love. And, and, I am not exaggerating. There are perhaps better sounding headphones out there, but I have not tried them. So, my tests is limited to what Guitar Center sells for $89 to $199 and my ears.