That is a very difficult question to answer. Understood.
In my HUMBLE opinion I would say it's to do with the capability of the driver, to accuratly reproduce how you tune it/EQ it.
I am a student of this game and I am barely 10% at best into actually understanding.
I like how nobody is able to REALLY answer this yet mind.
I just didn't bother to answer really. I have no idea what other headphones you owned before or what your preferences are.
I got into headphones with the Focal Elegia.. upgraded soon to the Dan Clark Aeon 2 noire, a while ago I got the Meze Liric.
I EQ all my Headphones.
I prefer planar magnetic drivers and closed back headphones.. the next person will be all over open back headphones.
I've never tried your AKG headphones.
My gear stayed the same and will probably not change at all. (Singxer SA1 + Cambridge CXN v2 & SMSL D300 and SP400)