It makes sense comparing Yamaha RX-A780 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, Yamaha RX-A780 has 7.2 versus 2.0 for Onkyo TX-8020. Regarding power, then RX-A780 has such a W/Ohm ratio - 95/8, 160/4 when TX-8020 has a power of 90/6. The THD is 0.06% for the RX-A780 but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, Burr-Brown 384 KHz/32-bit for RX-A780 and 192 KHz/24-bit for the TX-8020. Only the RX-A780 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 RX-A780 has Bluetooth support. The Yamaha RX-A780 has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the RX-A780 supports Spotify. Only the RX-A780 provides HDMI signal transmission in standby mode. The RX-A780 can scale the input HDMI signal, unlike the TX-8020. Dolby Vision technology found support only on the RX-A780. Only the RX-A780 supports HDMI Audio Return Channel (ARC). The HDMI eARC is available only on the RX-A780. Of the two receivers in our comparison, HDMI CEC is present in only the RX-A780. These compared receivers have a built-in phono stage for connecting a vinyl player. An ECO mode is only available for the RX-A780. The setup assistant will help you configure Yamaha RX-A780.
Only the RX-A780 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the RX-A780.
The Yamaha RX-A780 is better receiver in this comparison. Check Yamaha RX-A780 price