[LG V20 Questions & Answers] [M]otortrend:
1). The V20 and G5 have similar screens. Obviously the V20 has 0.5" size advantage but is also much bigger in general, so it is not easy to use with one hand. In terms of pixel density, brightness and colors I can't tell much of a difference. If I had to pick, however, the V20 would win any day.

2). Both phones have single, bottom-firing speakers, which I am sure you already know. What this means? Both of them are just OK. They are basically on the same level with no noticeable differences. They are not bad by any means-- plenty of phones have worse bottom firing speakers, like the Samsung Galaxy S7 line-- but for an Audio- and Cinematography- focused phone like the V20 you'd expect the speakers to match the quality of the 3.5 millimeter headphone jack. If you are dead-set on getting good (or at least better) speaker performance on the V20, you can remove the bottom bezel and take off the dust cover that LG glued onto the speaker grille. I have never tried it, because it is a dust cover after all, but if you are willing to get that speaker quality boost then there are some online instructions on how to do so.

3). Build quality is MUCH better for the V20. It's not water resistant, but it has that MIL-STD-810G drop resistance that both the V10 and the recently released V30 have. The G5, in contrast, does not. Because the phone is so big, it also weighs more, and the removable battery mechanism is also much better, both in form and function. The metal is cool to the touch and the bezels, though noticeable, are actually quite thin. Just don't ask me why LG decided to put an earpiece on the top bezel instead of a speaker, because that would have rounded off the whole package. The G5 in comparison just feels cheap and insignificant. This is, of course, completely subjective, but I have always appreciated the look and feel of the V20. The S8 and G6 might look better to most people, but the V20 is not unlike a BMW M5- it looks like a regular sedan but it hides some serious stuff under the hood.

4). The G5 wins if you plan on using either device with one hand. That said, the V20 is HUGE- much bigger than the bezel-less dwarfs we see in 2017. Unless you have mammoth hands, the V20 is best operated with both hands-- not an issue for me, but for subway warriors, it could prove to be a challenge. The G5 is just smaller, and because it feels so cheap you don’t really worry about dropping it- ironic because the V20 has the 810G drop resistance, not the G5. The G5 is more practical for everyday usage, but the V20 feels better in the hand. Regardless, I would install a case on ANY phone I buy, because these are devices you are spending 250-300 dollars for.

5). I haven’t tried the B&O H3 headphones so I can’t say. As for the headphone jack- this is where the V20 shines. Basically the headphone jack includes a dedicated Digital-to-Audio Converter (LG calls it the “HiFi Quad DAC”) and Amplifier that is able to drive high impedance headphones to the degree that matches most standalone music players- DAPs that can cost in excess of 500-1000 dollars. I only have a pair of Phillips SHP9500s- 32 ohm impedance so they are not, by definition, “High Impedance” (the V20 adjusts DAC output based on the type of headphone connected, and 50 ohms is when the “High Impedance” mode kicks in), but the difference in audio quality and loudness is certainly noticeable.

6). I’d say the audio quality is about as good as the G5 with the B&O HiFi DAC module. It’s good to me, but I don’t have the audiophile grade headphones so I can’t really say. But it is certainly better than everything else on the market right now (except the V30, obviously), so there is that re-assurance that the V20 will play your music the way it was meant to be played.