It makes sense comparing Pioneer Elite VSX-LX304 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 VSX-LX304 has 9.2 versus 2.0 for Onkyo TX-8020. Regarding power, then Elite VSX-LX304 has such a W/Ohm ratio - 100/8, 225/6 when TX-8020 has a power of 90/6. The THD is 0.08% for the Elite VSX-LX304 but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, AK4458 384 KHz/32-bit for Elite VSX-LX304 and 192 KHz/24-bit for the TX-8020. Only the Elite VSX-LX304 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 Pioneer Elite VSX-LX304 can connect to the Internet via WI-FI. Only the Elite VSX-LX304 has Bluetooth support. The Pioneer Elite VSX-LX304 has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the Elite VSX-LX304 supports Spotify. Only the Elite VSX-LX304 provides HDMI signal transmission in standby mode. The Elite VSX-LX304 can scale the input HDMI signal, unlike the TX-8020. Dolby Vision technology found support only on the Elite VSX-LX304. Only the Elite VSX-LX304 supports HDMI Audio Return Channel (ARC). Unfortunately, HDMI eARC is not available on monitored devices. Of the two receivers in our comparison, HDMI CEC is present in only the Elite VSX-LX304. 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 VSX-LX304.
Only the Elite VSX-LX304 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the Elite VSX-LX304.