Both products are great at delivering an immersive sound experience. The main differences are related to the acoustic performance. While both provide an immersive experience, sound great and have similar feature sets, the Smart Soundbar 900 will play louder and deeper than the Smart Soundbar 600 and also uses PhaseGuide technology, which provides an even more immersive experience. Smart Soundbar 600 has 5 speakers in total, while the Soundbar 900 has 9 speakers in total. The Bose Smart Soundbar 900 also includes ADAPTiQ audio calibration technology, which adjusts the sound of the soundbar to best fit your room, regardless of the shape or furnishings.