It makes sense comparing Marantz SR6014 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, Marantz SR6014 has 9.2 versus 2.0 for Onkyo TX-8020. Regarding power, then SR6014 has such a W/Ohm ratio - 110/8, 185/6 when TX-8020 has a power of 90/6. The THD is 0.08% for the SR6014 but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, AK4458 384 KHz/32-bit for SR6014 and 192 KHz/24-bit for the TX-8020. Only the SR6014 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 SR6014 has Bluetooth support. The Marantz SR6014 has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the SR6014 supports Spotify. Only the SR6014 provides HDMI signal transmission in standby mode. The SR6014 can scale the input HDMI signal, unlike the TX-8020. Dolby Vision technology found support only on the SR6014. Only the SR6014 supports HDMI Audio Return Channel (ARC). The HDMI eARC is available only on the SR6014. Of the two receivers in our comparison, HDMI CEC is present in only the SR6014. These compared receivers have a built-in phono stage for connecting a vinyl player. An ECO mode is only available for the SR6014. The setup assistant will help you configure Marantz SR6014.
Only the SR6014 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the SR6014.
The Marantz SR6014 is better receiver in this comparison. Check Marantz SR6014 price