I am sure both will be good choices. My backup is a 6P and I have never owned an LG device so I went with LG. I bought the HTC 10 for similar reason, the DAC. It is not smoke and mirrors and the sound of the HTC 10 was phenomenal. I presently use my 6P, crappy audio. Again understand I have an AK DAP that I paid 1000+ for, so it is kinda my thing. I also have many iem's and headphones, with the B&O they are offering as the lesser quality pair, so I will probably sell those. I also listen to a lot of lossless files and stream Tidal. It is nice to have storage(sd) to store my music on. I understand they have a 128gb version which you are paying 120.00 for. I just sold an EVO + 256gb U3 card for 130.00.
I love the Nexus line, particularly the 6P, so I am sure the Pixel will be good. I would have been more excited if Huawei was the manufacturer but they declined. If you want quicker updates, realistically think of how many actual updates there are, I would choose Google. Without reviews, the features are underwhelming, when comparing to a Note7 price/feature ratio.
In my mind, it is better to pay a restocking fee than be stuck with a device I don't want. If need be I will return the V20 and order the Pixel. Unfortunately, there aren't a lot of new phones out there that grabbed me.