Onkyo TX-RZ710 vs Harman Kardon AVR 1510 comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Onkyo TX-RZ710 has 7.2 versus 5.1 for Harman Kardon AVR 1510. Regarding power, then TX-RZ710 has such a W/Ohm ratio - 175/6 when AVR 1510 has a power of 75/8, 75/6. The THD is 0.08% for the TX-RZ710 but 0.09% for the AVR 1510.
Characteristics of digital to analog converter (DAC) are different, AK4458 384 KHz/32-bit for TX-RZ710 and 192 KHz/24-bit for the AVR 1510. 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. Only the TX-RZ710 has 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 1510. The HDR standard - Dolby Vision is not supported by these receivers.
The Onkyo TX-RZ710 has 8/2 HDMI inputs/outputs versus 4/1 HDMI connectors of the Harman Kardon AVR 1510. The HDMI Audio Return Channel (ARC) feature supports both devices. Unfortunately, HDMI eARC is not available on monitored devices. Of the two receivers in our comparison, HDMI CEC is present in only 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. Unfortunately, the setup assistant is not available in each of the models.
Only the TX-RZ710 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the TX-RZ710.