It makes sense comparing Vizio M21d-H8 vs LG SL9YG because they both are able to give some premium features. Based on our rating, M21d-H8 has a total rating of 5 out of 10 versus 8 for SL9YG. The competitors' control buttons are different: power, volume down, volume up, source, Bluetooth and power, volume down, volume up, play/pause, microphone, respectively.
Both soundbars have active amplification type. A significant difference between the units in the number of channels, the Vizio M21d-H8 has 2.1 versus 4.1.2 for the LG SL9YG. Only the Vizio M21d-H8 has a built-in subwoofer. The Vizio M21d-H8 got our rating of 5 out of 10, and the LG SL9YG 8 for its audio features and specs.
Soundbars do not have AirPlay support. Spotify support is available on the SL9YG.
Only the LG SL9YG can connect to the Internet via WI-FI. Rivals from our review have Bluetooth support. Each soundbar has 1/1 HDMI inputs/outputs. The HDMI Audio Return Channel (ARC) feature supports both devices. Both soundbars have a USB connector. For connectivity, the M21d-H8 received a rating of 6/10 versus 7/10, respectively.
App control is available for the SL9YG. A built-in microphone is present in each model. Multi-room is only available for the LG SL9YG.
Only the SL9YG has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the SL9YG. For multichannel surround Vizio M21d-H8 got a rating of 5, and LG SL9YG 8 out of 10.