The Denon AVRX4400H vs Pioneer VSX-LX503 comparison proves that these receivers have many common features.
Considered AV receivers have the same number of channels 9.2. Regarding power, then AVRX4400H has such a W/Ohm ratio - 125/8, 165/6 when VSX-LX503 has a power of 120/8, 230/6. The THD is 0.05% for the AVRX4400H but 0.08% for the VSX-LX503.
Characteristics of digital to analog converter (DAC) are different, 192 KHz/24-bit for AVRX4400H and AK4458 384 KHz/32-bit for the VSX-LX503. Both the AVRX4400H and the VSX-LX503 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 Denon AVRX4400H has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Spotify can be used on each receiver. The AVRX4400H can work with the audio stream from Deezer, TIDAL, Pandora,iHeart Radio, Sirius XM, Sound Cloud, Napster, and the VSX-LX503 can receive a content from Deezer, TIDAL, Pandora, TuneIn Radio. 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. Both rivals can scale the resolution of the incoming HDMI signal. The HDR standard - Dolby Vision is supported by these receivers.
The Denon AVRX4400H has 8/3 HDMI inputs/outputs versus 7/2 HDMI connectors of the Pioneer VSX-LX503. The HDMI Audio Return Channel (ARC) feature supports both devices. The HDMI eARC is available only on the AVRX4400H. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. Both models support the standard HDCP 2.2. These compared receivers have a built-in phono stage for connecting a vinyl player.
Each of the AV receivers from our review supports 3 Multi-room zones. The AVRX4400H supports voice control via Amazon Alexa, Google Assistant, Siri, Josh.AI, and the VSX-LX503 - Google Assistant. An ECO mode is only available for the AVRX4400H. Both AVRX4400H and VSX-LX503 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.