What's the difference? No streaming services support lossless audio anyways. And Vizio's eARC implementation is screwed up- only PCM 2.0 support. Hopefully something they'll eventually fix, but this is Vizio we're talking about here so who knows?... unless you use the AVR/pre-pro as your central hub, and not the TV. eARC hasn't proven to be the most reliable solution for many combinations of equipment. Additionally, the newest Vizio TVs appear to have some eARC issues of their own (not that I've experienced, I don't use it. Purely basing that off back scroll in this thread so YMMV).
That being said, I would agree with you 100% if eARC were in a truly working state across all the gear combinations people have.
Disclaimer: I have a bunch of ATV4Ks in the house, but I also have a Shield Pro arriving tomorrow.
Also, no 24Hz on the ATV 4k. I can't stress that enough, and no bitstreamed audio on the ATV4K. I had mine sitting in a box for a year and once I got a TV with Airplay support I just sold it.
That said on a large TV like this one the AI Upscaling makes a big difference, especially for lower-quality streaming services like CNN/NBC/ABC, etc, which tend to stream a lot of their content in 720p/29Hz.