One factor that might make a difference is what your using to drive them, the 48-Ohm MA900 should easy work with portable audio devices (DAP & smartphones) or computer audio.
Where as the AKG K612 Pro is 120-Ohm and might like a little more juice, so computer audio to modern A/V receivers would would be good sources for the K612.
If you already have a decent headphone amplifier, then either headphone would work.
Well I started with the ATH-M50's and then took those to use for the office and travel since they were closed back and a bit more isolated. That led me to getting the X1's for home use - about 90% PC and 10% portable with iphone/SGS4. But I'm looking to keep the X1's for the more relaxed at home music listening sessions and wanted to replace them with something that will be used solely for PC.
The biggest interest is in a neutral sound with a good soundstage and positional queues - I currently have a Magni/Modi stack and a Xi-Fi titanium (which I'm not using because for some reason my motherboard refuses to detect it). I figure the Magni should be good enough to drive the K612 and Ma900?
Now it's just a matter of which of the two I really would be happier with. I know I'll probably be thrilled with the new addition whatever it may be, but as far as PC it's mostly for gaming (FPS/RTS/Moba/MMO) and background music (spotify) during non-competitive gaming sessions.
Now the kicker is ... which of these two is gonna be in my cart when I click submit on my amazon order?
Quick edit - as far as music goes I mostly listen to house/DNB/Rock/Classical/Alternative/80's - pretty much anything other than a lot of current pop or country... Not sure if that affects the decision though considering my emphasis is on what will give me the most satisfaction in gaming and competitive gaming scenarios lol.
Edited by RoosterMKV - 3/18/14 at 2:02pm