It makes sense comparing Yamaha RX-S602 vs Denon AVR-X4400H because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Yamaha RX-S602 has 5.1 versus 11.2 for Denon AVR-X4400H. Regarding power, then RX-S602 has such a W/Ohm ratio - 80/8, 125/6 when AVR-X4400H has a power of 125/8, 165/6. The THD is 0.08% for the RX-S602 but 0.05% for the AVR-X4400H.
Characteristics of digital to analog converter (DAC) are different, Burr-Brown 384 KHz/32-bit for RX-S602 and AK4458 384 KHz/32-bit for the AVR-X4400H. Both the RX-S602 and the AVR-X4400H support Bi-amping. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
WI-FI modules have the same characteristics: 2.4/5GHz. 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 RX-S602 can work with the audio stream from Deezer, TIDAL, Pandora, Napster, SiriusXM, Qobuz, and the AVR-X4400H can receive a content from Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud. 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 AVR-X4400H can scale the input HDMI signal, unlike the RX-S602. Dolby Vision technology found support only on the AVR-X4400H.
The Yamaha RX-S602 has 4/1 HDMI inputs/outputs versus 8/3 HDMI connectors of the Denon AVR-X4400H. The HDMI Audio Return Channel (ARC) feature supports both devices. The HDMI eARC is available only on the AVR-X4400H. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. The RX-S602 supports the protection of digital content of the standard HDCP 2.3, versus HDCP 2.2 in the AVR-X4400H. The AVR-X4400H has a built-in phono stage for connecting a vinyl player.
The RX-S602 supports 2 Multi-room zones, versus 3 for the AVR-X4400H. The RX-S602 supports voice control via Amazon Alexa, Google Assistant, and the AVR-X4400H - Amazon Alexa, Google Assistant, Siri, Josh.AI. It is also worth noting that the ECO mode is presented in each of the receivers. Both RX-S602 and AVR-X4400H can be configured using the Setup assistant.
Only the AVR-X4400H has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the AVR-X4400H.