Tried your songs.
First:
In my view, mixing is not that simple as picking the 'right' headphone and let it do the job. Whatever headphone you finally pick, you'll have to understand its sound signature.
Some examples:
- AKG K/Q 701/2 have typically forward upper midrange (around 2 kHz)
- Beyerdynamic DT880 have slightly bright treble around 6 kHz - 9 kHz
- HD650 has slightly boosted bass and slightly recessed treble
Each headphone, even T1, even HD800, even SR009 has sort of a personality, and you must know it very well if you want to take full advantage of its potential.
More so, I think it's important to try the music in a typical system after mixing. With 'typical system' I mean, try your music with the kind of headphones and/or speakers that you think most of the consumers will be using for that music/genre.
Very little people (read no one) is picking Q701 or DT880 for dubstep, trance and so...
On the other hand there's plenty of people picking V-Moda M100, Yamaha Pro 500, Fidelio X2, Yamaha EPH-100 for those genres.
If you pick Q701 and make music that sounds great trough Q701, then your music will sound far too boomy on the V-Moda M100 pair of the more typical listener.
That's a decission you have to make at some point. Mixing electronic music for most consumers or mixing for a vast minority of (uber) (neutralish) audiophiles using K702 or Mr. Speakers Ether for dubstep/trance/etc.
If you aim to the massive consumer market, you still need the neutralish system (ie, Q701/DT880/K612) to pick up details and flaws but you also need to understand that you are looking for a slightly 'bass light' sound when you mix, so it will sound just right when someone plays it on a more typical system (headphones/speakers)
Tried the songs with K702 and DT880/250, both are very revealing headphones in their own fashion. DT880 is just a tad more extended at both ends which is good. There's always a trade off. While K702 sounds wider with better separation and placement, DT880 is not far behind and in exchange it's more neutral/uncoloured across the spectrum. DT880 is probably better for tonality, while K702 is better for soundstage.
Bass?
Both tight and defined.
DT880 is slightly fuller, while K702 is more on the dry side of things.
Sub-bass is just a tad more refined on the AKG to my ears, but can be slightly shy.
I wouldn't pick any of these headphones to just relax and play your music, although I would pick any of them for the mixing stage.
I think DT880 would be my pick, despite being less capable with soundstage due to its more extended response and more neutral upper midrange.
K612 Pro (same would apply to Sennheiser HD600) might fall between the two worlds, not sort of an analytical tool like K702 or DT880/250, but still neutralish, detailed, and hopefully closer to more typical systems (warmer).
As stated earlier, you can't go wrong with either.
You can think it this way, if you want a great tool, then go Q701 and remember to go back and forth between Q701 and a more typical (warmer and more forgiving) system to understand how music should sound on Q701 in order to sound great on a more typical setup.
If you want a very good tool that's also very good for listening pleasure and a tiny bit closer to the typical consumer system, then go K612 Pro. (I think this is a safe bet)
If your budget also allows DT880/250, it's also very nice for the task and worth considering. Very neutral across the board, more solid in construction than both AKGs and comes with the classic Beyer carrying case.
At the end of the day, only you can decide what to pick. Just don't get crazy trying to find a perfect solution, there's always a trade off.
You could have been enjoying a great pair of headphones all these days and you are not!
What are you waiting to join this wonderful crew?