I personally find the akg k550 to be clearly better,it has a more neutral sound signature,better tonality.Actually the akg k550 is among the best closed I've heard in this price,along with the shure srh 840.(which I don't find it to be that different compared to k550).
Sony are not bad,but I find them too warm and coloured...and there is a lack of treble presence.They have nice imaging and smooth,grain free sound to my ears,but they sound a bit unnatural,too warm and full in the mids/midbass.I'll give them more burn in time to see if they change.
It's a shame because it's the best of all the closed i have right now (shure srh840,akg k550,krk kns 6400),in terms of looks and comfort...I wish it had the sound of one of these three or something close to their sound anyway,but I guess you can't have everything in one headphone...