the way i see it
m50 = good at representing 100hz synth bass
dt770 = great at representing an 808
I own an M50 and also love dubstep. I can tell you right now that the M50 is perfect for the dubstep genre.
The M50, however, is not the most convenient headphone to use on-the-go. Sure, it's foldable, comes with a nice carrying pouch, and your iPod can easily play it without needing a portable amp.......but it is also big, heavy, and comes with a very long cord.
Oh, I had SC FMJ's before. They kept on breaking - which led me to research on ear/headphones, which led me here and to the M50. The M50's are definitely a big step up in build quality over the SC products.
Most of what is stated in the above post is incorrect. I own the ATH-M50, while my officemate has the Beyerdynamic DT770 80ohm. We both have them on right now. I asked him to borrow them in order to compare them and I've switched back and forth for the past 15 minutes. Source music: FLAC files fed to an iBasso D2+ Boa DAC/Amp. Files I've tried are acoustic jazz, nu-jazz (St. Germain, Nicola Conte), Classic Rock (Allman Brothers Band), Blues (BB King - Live at the Regal).
Both are IMO amazing headphones. However their biggest difference is not the bass. With all the music I've tried, the M50 are FAR from being bass shy. They have a very precise and deep bass with a characteristic fast decay. I find the DT770 to have a slightly slower bass with a slightly slower decay. The bass on the DT770 seems to "envelope" more the listener, while on the M50 seems to have a more "uni-dimensional" nature. In both cases, the bass is rather balanced and does not ruin the other frequencies IMO. Overall I would say the spatial aspect of the reproduction is slightly better on the DT770, while PRat (pace, rhythm and timing) is better on the M50. Given the genres I listen to, I'd say I would be happy with both. Somebody listening to more classical/ambient etc should probably lean more towards the DT770.
Now, I don't know what a basshead is, and what a basshead listens to, but if you want ACCURATE and hard hitting bass for genres like jazz, blues, rock, classical, ambient, trip-hop, etc, the M50 have it. More bass than my M50 have, and I would totally hate them because the mids and treble would be ruined.
If you're looking for a tool to pump almost exclusively 40 hz tones in your ears without regard for the rest of the frequencies, then you shouldn't be looking at hi-fi/monitoring headphones at all - neither M50 nor DT770 will do what you want.
Actually your posts go well together. One of you said the DT 770 has a lot more bass, which I visualize as being slower, more all-over the music - maybe a bit bleeding into the mids too? I've felt like that sometimes, where I can always sense that slow vibration in my ears, with a note I can barely hear, I just assumed they extended very low. Maybe it's not much about the ammount of bass, but more the way it's displayed?
There is absolutely no way on God's green earth that I would choose either of those over the DT440. They arent the bass cannons that so many on Head-Fi seem to want, but the Beyers would smoke many cans in the mid-fi realm. They are under-appreciated here because they dont leap out at you like some other cans, but the OP did ask for suggestions and thats my suggestion.