It makes sense comparing Denon AVR-S750H vs Onkyo TX-NR595 because they both are able to give some premium features.
Considered AV receivers have the same number of channels 7.2. Regarding power, then AVR-S750H has such a W/Ohm ratio - 75/8, 110/6 when TX-NR595 has a power of 80/8, 170/6. The THD is the same and is 0.08%.
Characteristics of digital to analog converter (DAC) are different, AKM 192 KHz/32-bit for AVR-S750H and AKM 384 KHz/32-bit for the TX-NR595. Only the TX-NR595 supports Bi-amping feature. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
Both models have the ability to connect to the Internet via WI-FI. Rivals from our review have Bluetooth support. The Apple Music service is implemented on considered devices: AirPlay, AirPlay 2. Spotify can be used on each receiver. The AVR-S750H can work with the audio stream from Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud, Mood Mix, and the TX-NR595 can receive a content from Deezer, TIDAL, Pandora, TuneIn Radio.
Both AV receivers support HDR10 technology (High dynamic range). 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-NR595 can scale the input HDMI signal, unlike the AVR-S750H. The HDR standard - Dolby Vision is supported by these receivers.
The Denon AVR-S750H has 6/1 HDMI inputs/outputs versus 6/2 HDMI connectors of the Onkyo TX-NR595. The HDMI Audio Return Channel (ARC) feature supports both devices. The HDMI eARC is available only on the AVR-S750H. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. The AVR-S750H supports the protection of digital content of the standard HDCP 2.3, versus HDCP 2.2 in the TX-NR595. These compared receivers have a built-in phono stage for connecting a vinyl player.
Each of the AV receivers from our review supports 2 Multi-room zones. The AVR-S750H supports voice control via Amazon Alexa, Google Assistant, Siri, Josh.AI, and the TX-NR595 - Google Assistant. An ECO mode is only available for the AVR-S750H. Both AVR-S750H and TX-NR595 can be configured using the Setup assistant.
Both devices have support for Dolby Atmos multichannel audio format. The surround sound technology DTS:X is supported by devices under review.