The main differences are related to the acoustic performance of the Bose Smart Ultra Soundbar. They both support Dolby Atmos encoded content and optimise content that is not Dolby Atmos encoded through proprietary TrueSpace spatial processing technology to sound just as spacious and immersive. The Bose Smart Ultra Soundbar also includes ADAPTiQ audio calibration technology, which adjusts the sound of the soundbar to best fit your room, no matter the shape or furnishings. The Bose Smart Soundbar 600 offers great dialogue intelligibility, spacious sound, but it doesn’t come with ADAPTiQ. While it is still a great performing system, the sound is not as loud, as deep, or as spacious as the Bose Smart Ultra Soundbar.