It makes sense comparing Denon AVR-X8500H 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, Denon AVR-X8500H has 13.2 versus 2.0 for Onkyo TX-8020. Regarding power, then AVR-X8500H has such a W/Ohm ratio - 150/8, 250/6 when TX-8020 has a power of 90/6. The THD is 0.05% for the AVR-X8500H but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, AK4490EQ 768 KHz/32-bit for AVR-X8500H and 192 KHz/24-bit for the TX-8020. Only the AVR-X8500H 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 Denon AVR-X8500H can connect to the Internet via WI-FI. Only the AVR-X8500H has Bluetooth support. The Denon AVR-X8500H has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the AVR-X8500H supports Spotify.
Only the Denon AVR-X8500H has support for High dynamic range (HDR). Only the AVR-X8500H provides HDMI signal transmission in standby mode. The AVR-X8500H can scale the input HDMI signal, unlike the TX-8020. Dolby Vision technology found support only on the AVR-X8500H. Only the AVR-X8500H supports HDMI Audio Return Channel (ARC). The HDMI eARC is available only on the AVR-X8500H. Of the two receivers in our comparison, HDMI CEC is present in only the AVR-X8500H. These compared receivers have a built-in phono stage for connecting a vinyl player. An ECO mode is only available for the AVR-X8500H. The setup assistant will help you configure Denon AVR-X8500H.
Only the AVR-X8500H has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the AVR-X8500H.