Cause of different sound between dacs

Just reading about the Esoteric K 03.
How does the output differ from the Alpha dac, for example.
What exactly is responsible for any sound difference assuming the balance of the systems identical?
Still confused by digital.
I am not able to audition the two. Perhaps someone with experience can comment?
I was very surprised at how much better my K03 sounds, compared to my Berkeley Alpha Dac (1st one). It has much more detail, more resolution, deeper/wider soundstage - I can go on and on - it was just 'better' in every plane. I am thinking power supplys, dacs and analogue output stage are all superior.
The power supply and analog circuit have the biggest impact on the sound.