Real upfiring speakers do a better job, so the Atmos experience is obviously better with the Arc.

The Arc features two upfiring drivers to create the height effect in an Atmos soundtrack while the Beam uses software to virtually create those samet sounds. Speaking of Atmos, which is Dolby’s spatial audio format, and what allows you to hear surround sound coming from just one speaker, there’s a significant difference between how the two soundbars produce it. Dolby Digital Plus is an advanced surround sound audio technology that enables the Dolby Audio experience across home theaters, smartphones, operating systems, and browsers. And the second generation of the Beam has even more audio detail along with Atmos support. More Dolby Digital Plus Home Theater 7.6.5.1. You’ll have a hard time believing what big sound can come from such a small soundbar. This provides the Arc with a wider sound stage and more bass as well as louder sound. In fact, there are 11 total drivers in the Arc - three tweeters and eight woofers - while the Beam crams in five drivers - one tweeter and four woofers. Given its much larger footprint, it should come as no surprise that the Arc houses more drivers than the Beam. Both these soundbars will deliver high-quality Sonos sound, but the Arc does have a few advantages –which makes sense considering its price point.

Dolby digital plus home theater driver