Which is completely useless as the single DAC chip itself was having noise levels way below audibity threshold. 2 chips - marketing; simple as that.
To my ears dual chip devices sound better; fuller sound, bass is stighter and fuller, and extended sound stage. I think a lot depends on the other equipment in the chain. I have just finished testing that theory using the following scenarios:
Scenario 1: SMSL-su10 -> Musical Paradise MP-701 MK2 tube preamp->Classe CA100 amp-> KlipschHorn full range speakers
Scenario 2: SMSL-su10 -> Musical Paradise MP-701 MK2 tube preamp->Classe CA100 amp-> Klipsch Cornwall full range speakers
Scenario 3: SMSL-su10 -> Musical Paradise MP-701 MK2 tube preamp->Classe CA100 amp-> Klipsch Heresy bookshelf speakers
With the speakers being the only difference.
Scenario 1 and 2 substantially sound better than scenario 3 (culprit the smaller bookshelf speakers can not reproduce the full range of the sound). Scenario 1 and 2 sound almost the same, with scenario 1 having a slight edge.
Repeated the above by simply changing the DAC with a Topping D90. It is right away clear to my ears that the topping provides a thinner sound, smaller sound stage, more prominent highs with the equipment of scenario 1-2, but scenario 3 sounds the same to my ears regardless of the DAC.
Repeated the above again by replacing the DAC with a FIIO M17 (the M17 uses the same dual ES9038 pro chips as the su-10). Again, right away I can hear a fuller sound reproduction, and bigger sound stage, however the M17 sounds slightly clearer that the su-10, but both are substantially better that the single chip Topping D90 when listening via the full range speakers, again no discernable difference when using the bookshel speakers.
My conclusion, as proven above, of course you won't hear any difference if the other equipment in the chain have limitations.