Clearly I'm not a pro at this but here goes something...
After not feeling 100% satisfied with my T 70's I wanted a little more Umph in the bottom end so I found great deals on the DT 770/80 ($149 new eBay- Contact me if you want the link they have more plus a 60 day return policy... Yes 60 days no questions asked) and the COP ($189 Amazon-Currently you can get them for $162). I'm still not finished with the testing but so far I do agree with what some have said so far. The DT770/80's have a much crisper sound than the Custom One Pro's but thats not a knock against the COP which I like but it is what it is. I actually put them up against my HIFI-780's and the COP won hands down and I sold my 780's which again I loved.
Now to the direct comparison and I'll break this down to make it simple and quick
Comfort: Tie - The COP's are super light weight, zero clamp, and soft leather pads while the 770's are a little heavier with a slight clamp but the Velour pads are amazingly comfortable. Not as comfortable as the DT 990/250's but honestly nothing I've ever worn before can compete with the comfort of those bad boys. I told my wife I was going to make a Velour jumpsuit out of those pads... She shook her head and quickly walked away.
Portability: COP - 16ohm speakers... Nuff said. You need to amp the 770's for them to reach their full potential but running them through my Macbook Pro I got great results. My e11 does ok but I think its time for a change but not sure what to change to, a little help would be nice for those of you that are amp savvy
Soundstage: DT 770/80 - This is where the tide changes and stays in favor of the 770's. The sound stage is amazing for a closed can and it has the best depth of any headphone I've tested/owned. Using them with my Astro Mixamp 5.8 is redonk!! The bass you would think would get in the way and yes its clearly there but it doesn't get in the way at all. Playing BF3 on my 360 good luck sneaking up on me because the distance and direction is better than the best "gaming" headsets I've tested. I'm a sneaky C4 junky so sitting and waiting for tanks has never been easier. And when the boom comes the bass is eye popping and always giggle inducing. Now on the other hand the COP are no slouches either, but the bass feels a little muddy and the separation is good but cant compete but honestly, what can??
Highs: DT 770/80 - They just come through cleaner and more relaxed but neither has the it factor in this area. The COP's are brighter and seem to pop out a little better but at the same time can get fatiguing at higher volumes. While I was A/B the two this was the biggest difference IMO. The COP's highs are right in your face aggressive and at times it feels like they're trying to hard. That is where the 16ohm ratings are at a disadvantage because being that easy to run is nice an all until you wanna turn the volume up and it feels like your ear drums are gonna pop.
Midrange: DT 770/80 - Not as recessed which will be shocking to most that know the 770's because they have pretty recessed mids in the first place but for the type of music I listen to with these they work. If I wanted to High and Mid myself to death I have the T 70's for that :) I think the real problem with the midrange on the COP's is the the fact the the highs and lows just simply overwhelm the mids and because the separation isn't that great it makes it hard for the mids to come through.
Bass: DT 770/80 - This one I thought was going to be a toss up but it was not. At first when you pick up the COP's of course the first thing you want to do is crank the switch to the 4th and final position throw on some dub and get to work!! And at first its like yes this is nice, but once your ears stop ringing from all the Robot sex you start to listen and notice how bloated the bass is and how hard its working to keep up with the music you're putting through it. At higher volumes notes were missed, drops were sloppy, and general sadness started to kick in. Once the volume was returned to a normal state things improved greatly. Now the 770's on other hand were cool and collected regardless of what I put them through and at all volumes. The levels didn't increase with the volume and they remained steady throughout the entire process. What was funny was that the only time I felt they were limited was when I put them through my e11 hence the reason I say its time to move on. Soundstage was reduced and the bass got bloated regardless of the settings. Clear winner in the category.
Isolation and sound leakage: Tie - Isolation goes to the 770's but The COP's do a better job at keeping all the sound in your head and not in your neighbors lap.
Overall thats 4 wins for the DT 770/80's 1 win for the COP's and 2 ties giving the clear and decisive win to the 770's. I like what Beyer did here with the COP's. They clearly were going for the commercial sound and if compared to the Beats and Sol's of the world they win hands down in almost every way possible except for being overpriced. Beats will win that battle almost every time.
Which one you buy is ultimately up to you and hopefully I gave you some useful information to make the choice a little easier and if I didn't oh well, at least I had fun in the process. Thanks for the read and please throw out your suggestions for a good portable Amp under $160 that will do a better job than the e11 or gives a different sound signature.
Thanks again and Take Care
P.S. I'm not to proud to bump myself if I have to :)