I needed to buy a decent closed headphone for music, movie and fps gaming. I bought these two to compare, but decided to keep the AKG K271 and return the Beyer DT770. Here are some of my impressions of the two. My sources: ripped FLAC or purchased MP3 320kbs -> E-MU Tracker Pre (same as 0202USB).
What follows are entirely subjective, also I don't believe in burn in, only that the ears get used to the sound overtime. Skip to the bottom to get the bullet points and avoid the ramblings.
Beyer Dynamic DT770 Premium 32Ω (bought used $180)
I prefer light and tightly wrapped bass with some punch. The DT770 has overblown and bombastic bass, mostly upper bass (150-300hz). I am incapable of listening to it without EQing the bass down. The abundance of bass sometimes drown out important details of the music on the upper ranges. The bass however packed a more satisfying punch than the AKG.
The midrange and upper frequencies are really beautiful and refined (when they are not muddled up by the bass), this is an incredibly detailed phones for the price. The mids are really smooth which works absolutely beautiful with female voices and strings. However, it does suffer from being too laid back, not upfront and as much body like AKG headphones. The highs are very clear, but maybe not very sweet sounding (I prefer a little coloring). It does not suffer from any sibilance.
I think the DT770 is not perfect for heavy rock and metal as far as electronic guitars, sure it will be very clear, but it will lack some aggressiveness due to laid back mids. The DT770 has a big soundstage and realistic layering. Its very comfy with the velour pads. It clamps tight and isolates well, but some people might get the suction feeling to their ears, but its not too bad and can get used to.
AKG K271 MKII 55Ω (bought new $150)
The bass amount for the K271 is just right for me. The bass is tight and can be punchy, but doesn't pack the power the DT770 can deliver. However, it goes low and gives satisfying drone or rumble which is good for movies and symphony music. If you need a lot of bass, these might deliver just barely enough unless you have a quality amp or a bassy source.
The mids are upfront, good for rock and metal. The highs are a bit sweeter sounding than the DT770, but it doesn't soar and less refined, and maybe a bit rolled off. The upper ranges overall are dryer sounding compared to the smoother DT770. Clearly the DT770 has more refinement and clarity. The soundstage and layering is clearly not impressive as the DT770 either. However, the K271 is just more present and sometimes more fun to listen to.
One of the important reason I prefer the K271 is that it doesn't feel and sound "closed" like the DT770. For one the headphone is lighter, it doesn't clamp as hard so no suction feeling, though that means it isolates a few decibel less. It's more comfortable to wear and I prefer balanced sound. That is not to say the DT770 is not as comfortable, as Beyer velour earpads are much nicer than the AKG velour pads, I just dislike the DT770 suction feeling.
Gaming: I think the DT770 is a poor candidate due to the bass muddling up the frequency range, unless your meaning of gaming is more bass = better. I play online fps games where I need to hear enemy footsteps, microphone voice over from teammates, all of the tiniest details, so I need a headphone with clarity across the whole range, not a bassy headphone. My games don't have EQing features and I'm not willing to buy a mixer for the DT770, therefore I have to go with the K271 for its versatility.
It is clear the Beyer DT770 has better build quality and more refined sound (after tuning) compared to the AKG K271. However, the K271 is more balanced across the freq chart and easier on my ears which is why I prefer it. I will miss most from the DT770 its larger soundstage and more realistic layering.
-powerful and too much upper bass, causes muddiness without EQing
-incredibly detailed, refined and clean mids and high, no sibilance ( + female voices, classical, ambient)
-mids are laid back ( - rock/metal)
-large soundstage and good layering
-very comfortable, nice velour pads
-good clamping force and decent isolation, but causes suction feeling to the ears
-good build quality, nice looking
-comes with 32ohms version which is easy driven by portables
-clean bass, can go low and gives satisfying drone/rumble ( + classical/movies)
-bass probably won't deliver a powerful punch without a good amp and/or source
-upfront and present mids ( + rock/metal)
-dryer upper ranges compared to smoother DT770
-overall balanced sound, not too much or little of anything, no sibilance
-soundstage and layering are ordinary, not impressive as DT770
-light in weight and doesn't clamp hard, can be worn for a long time
-might be driven loud by portable, but will need a good amp to achieve its potential