The Pioneer VSX-S520 vs Marantz NR1504 comparison proves that these receivers have many common features.
Considered AV receivers have the same number of channels 5.1. Regarding power, then VSX-S520 has such a W/Ohm ratio - 50/4 when NR1504 has a power of 50/8, 60/6. The THD is 0.09% for the VSX-S520 but 0.08% for the NR1504.
Competitors' digital to analog converter (DAC) is identical to 192 KHz/24-bit. None of the models 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 VSX-S520 can work with the audio stream from Deezer, TIDAL, TuneIn Radio, and the NR1504 can receive a content from Pandora, SiriusXM.
Only the Pioneer VSX-S520 has support for High dynamic range (HDR). HDMI signal transmission in standby mode is implemented in each of the devices. The VSX-S520 can scale the input HDMI signal, unlike the NR1504. Dolby Vision technology found support only on the VSX-S520.
The Pioneer VSX-S520 has 4/1 HDMI inputs/outputs versus 6/1 HDMI connectors of the Marantz NR1504. 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. Both models support the standard HDCP 2.2. The VSX-S520 has a built-in phono stage for connecting a vinyl player. A voice control is not available. An ECO mode is not present in each of the AV receivers. Both VSX-S520 and NR1504 can be configured using the Setup assistant.
Only the VSX-S520 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the VSX-S520.