ARC is limited to lossy DD+ but can contain and pass atmos metdata. Using ARC requires HDMI-CEC to be ON. This is where many problems start. So, somebody with a disc player connected directly to the TV would lose lossless Dolby TrueHD or DTS HD MA when sending audio to the receiver via ARC. They may end up with DD 5.1 or even PCM 2.0. Then eARC came along and solved a couple of problems. It aloud the return of audio to the receiver without activating HDMI-CEC and had the bandwidth to pass lossless audio from a disc player back to the receiver when connected directly to the TV. It does nothing for the DD+\/atmos signal from Smart TV apps. ALL streaming services use lossy DD+\/atmos signals at best and there are still some that only contain DD 5.1. If a Smart TV app has Dolby Vision\/Dolby Atmos support, great! Many still do not and Smart TV app stores have nothing on streamers like the Apple TV 4K, Nvidia Shield Pro or Roku Ultra. \n\nMany are still using TVs and receivers with just ARC. It may not be worth the hassle when having to deal with HDMI-CEC to use ARC. If a Smart TV app can pass atmos metadata from a DD+ stream using ARC, it might be worth it. If not, an optical connection may be sufficient passing DD 5.1. Oh, and currently, it is impossible to stream from a Smart TV while sending audio to the receiver via ARC\/eARC AND be able to make onscreen adjustments to the receiver. They'd need to come up with eARC+GUI so that could be possible. Presently, one needs to stop streaming and switch to the HDMI ARC\/eARC input so that the AVR's GUI can be made visible on the TV screen.