LOL the V20 cannot drive the HD800 anywhere near it's potential. Even the AK240 will be pushed single ended, balanced it has better results but still nowhere near the HD800 potential. If you are going to compare the V20 and AK240 then use them with earphones or headphones that can show their potentials instead of being underdriven. I liked the V20 when compared to other mobile phones but it still comes short when compared to dedicated DAPs like the AK240.
I've been using JH Roxannes listening to the G6 and the Granbeat. These can be driven easily by both players but I get more details and better staging and layering with the Granbeat. Mind you I am using the Roxannes with balanced out of the Granbeat but in AGC mode so should be same power as single ended.
For fun I did try both G6 and Granbeat with my HD800 but didn't like the sound from G6, underdriven and thin. It sounded better with the Granbeat from balanced out but still not to it's full potential. I admit I'm not a golden eared audiophile, just someone that enjoys music played right.
Don't read too much into the specs, ES9218 may share hyperstream II used in ES9038 but it's still a mobile dac like the ES9018. Whats's more important is how it's been implemented. ES9218 should have AVC as well but have seen no evidence of that being used on either of the LG phones. Don't confuse the desktop dacs like 9038 with the 9218. I compared the ES9018 desktop dac used in the iBasso DX100 with the ES9018 mobile dac used in the DX90 and there was huge difference in quality.
In the end you should let your ears decide which is better depending on the equipment you will use with it. Trying to run high impedance, hard to drive headphones with 2 portable players then deciding they both sound the same does not paint the true picture of their performance.