Hi I'm sorry to be contrary but I have owned and used both the lg v30 and the OnePlus 6 . Although the v30 clearly has the louder amp and quad DAC, I do most of my listening at low to moderate volumes through sensitive Iems (Shure se535 and se846) and I always found the v30 to have a bit of background noise during quiet passages of music. This led to me selling the phone, and I must say that the background of the OnePlus 6 is perfectly silent and I find the sound signature to be very neutral with a really good dynamic range. In addition, imho using the OnePlus 6 is an all round much better experience than the lg v30. Better quality oled screen and Fast and almost stock 8.1. major downside for me is no SD card slot. Had this phone since launch and seriously impressed so far.... It has overtaken the iPhone X as my daily driver for the time being (have also recently owned and returned the s9 plus and the pixel 2 XL - bothboth g phones in many ways, with class leading cameras but both not without problems).
Please no one take offense, just my honest opinions from personal experience .