It makes sense comparing Denon AVR-S510BT vs Onkyo TX-RZ710 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Denon AVR-S510BT has 5.2 versus 7.2 for Onkyo TX-RZ710. Regarding power, then AVR-S510BT has such a W/Ohm ratio - 75/8, 110/6 when TX-RZ710 has a power of 175/6. The THD is the same and is 0.08%.
Characteristics of digital to analog converter (DAC) are different, 192 KHz/32-bit for AVR-S510BT and AK4458 384 KHz/32-bit for the TX-RZ710. Only the TX-RZ710 supports Bi-amping feature. The Onkyo TX-RZ710 can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. Only the TX-RZ710 supports Spotify.
Only the Onkyo TX-RZ710 has support for High dynamic range (HDR). Compared AV receivers retain the quality of 4K/60Hz signal when transmitting from a source to a TV or projector. HDMI signal transmission in standby mode is implemented in each of the devices. The TX-RZ710 can scale the input HDMI signal, unlike the AVR-S510BT. The HDR standard - Dolby Vision is not supported by these receivers.
The Denon AVR-S510BT has 5/1 HDMI inputs/outputs versus 8/2 HDMI connectors of the Onkyo TX-RZ710. Only the TX-RZ710 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 only in the TX-RZ710. Both models support the standard HDCP 2.2. The TX-RZ710 has a built-in phono stage for connecting a vinyl player. A voice control is not available. An ECO mode is only available for the TX-RZ710. The setup assistant will help you configure Denon AVR-S510BT.
Only the TX-RZ710 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the TX-RZ710.