I have both now. I think the bass specific D40 ones are better. Both pretty good but the D40 better for the deeper tones. Haven't burnt them in but will soon.
I read this thread and bought the AT that were recommended.
I bought:
http://www.amazon.com/Audio-Technica-ATHM40FS-Precision-Headphones/dp/B0002D03ZW/ref=sr_1_3?ie=UTF8&qid=1293927118&sr=8-3
Should I have bought these instead...