It makes sense comparing Pioneer Elite SC-LX904 vs Onkyo TX-8020 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Pioneer Elite SC-LX904 has 11.2 versus 2.0 for Onkyo TX-8020. Regarding power, then Elite SC-LX904 has such a W/Ohm ratio - 140/8 when TX-8020 has a power of 90/6. The THD is 0.08% for the Elite SC-LX904 but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, ES9026PRO 384 KHz/32-bit for Elite SC-LX904 and 192 KHz/24-bit for the TX-8020. Only the Elite SC-LX904 supports Bi-amping feature. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Only the Elite SC-LX904 has Bluetooth support. The Pioneer Elite SC-LX904 has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the Elite SC-LX904 supports Spotify. Only the Elite SC-LX904 provides HDMI signal transmission in standby mode. The Elite SC-LX904 can scale the input HDMI signal, unlike the TX-8020. Dolby Vision technology found support only on the Elite SC-LX904. Only the Elite SC-LX904 supports HDMI Audio Return Channel (ARC). The HDMI eARC is available only on the Elite SC-LX904. Of the two receivers in our comparison, HDMI CEC is present in only the Elite SC-LX904. These compared receivers have a built-in phono stage for connecting a vinyl player. An ECO mode is not present in each of the AV receivers. The setup assistant will help you configure Pioneer Elite SC-LX904.
Only the Elite SC-LX904 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the Elite SC-LX904.