From Tom’s Guide website:

The biggest difference between Dolby Atmos and traditional surround sound is the use of channels. Audio over conventional surround sound is confined to 5.1 (five speakers, one subwoofer) or 7.1 (seven speakers, one subwoofer) channels.

Dolby Atmos ditches the channels and assigns the sound objects to a place. That means that if a sound occurs in the top right corner of the room, the audio will have spatial accuracy instead of being relegated to the right speaker. And because Atmos-compatible speakers have integrated upward-firing drivers, you have the added benefit of height.

I appreciate your comment, but with the Arc sounds still seem to come from the right speaker, left speaker, etc in Atmos,  not from the right or left of the room. It still sounds like dolby digital to me. I don't  hear sounds defined from one quadrant of the room but rather hear them from each speaker

Do you have the ability to test the same film in Dolby Digital 5.1 vs. Dolby Atmos? That’s the best way to determine the difference to your ears.

I will try that. Thanks for all your help and suggestions!