The Onkyo TX-RZ620 vs Denon AVR-X4100W comparison proves that these receivers have many common features.
Considered AV receivers have the same number of channels 7.2. Regarding power, then TX-RZ620 has such a W/Ohm ratio - 100/8 when AVR-X4100W has a power of 125/8, 165/6. The THD is 0.08% for the TX-RZ620 but 0.05% for the AVR-X4100W.
Characteristics of digital to analog converter (DAC) are different, 384 KHz/32-bit for TX-RZ620 and 192 KHz/24-bit for the AVR-X4100W. Both the TX-RZ620 and the AVR-X4100W support Bi-amping. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. The Apple Music service is implemented on considered devices: AirPlay. Spotify can be used on each receiver. The TX-RZ620 can work with the audio stream from Deezer, TIDAL, Pandora, TuneIn Radio, and the AVR-X4100W can receive a content from Pandora, SiriusXM. 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-X4100W can scale the input HDMI signal, unlike the TX-RZ620. The HDR standard - Dolby Vision is supported by these receivers.
The Onkyo TX-RZ620 has 7/2 HDMI inputs/outputs versus 8/3 HDMI connectors of the Denon AVR-X4100W. The HDMI Audio Return Channel (ARC) feature supports both devices. Unfortunately, HDMI eARC is not available on monitored devices. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. These compared receivers have a built-in phono stage for connecting a vinyl player.
The TX-RZ620 supports 2 Multi-room zones, versus 3 for the AVR-X4100W. A voice control is not available. An ECO mode is only available for the AVR-X4100W. Both TX-RZ620 and AVR-X4100W can be configured using the Setup assistant.
Both devices have support for Dolby Atmos multichannel audio format. A surround technology DTS:X is supported only by the TX-RZ620.