It makes sense comparing Denon AVR-X3500H vs Marantz NR1509 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Denon AVR-X3500H has 7.2 versus 5.2 for Marantz NR1509. Regarding power, then AVR-X3500H has such a W/Ohm ratio - 105/8, 135/6 when NR1509 has a power of 50/8, 60/6. The THD is 0.05% for the AVR-X3500H but 0.08% for the NR1509.
Characteristics of digital to analog converter (DAC) are different, AKM 192 KHz/32-bit for AVR-X3500H and 192 KHz/24-bit for the NR1509. Only the AVR-X3500H supports Bi-amping feature. 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 AVR-X3500H can work with the audio stream from Deezer, TIDAL, Pandora, TuneIn Radio, and the NR1509 can receive a content from Deezer, 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. The AVR-X3500H can scale the input HDMI signal, unlike the NR1509. The HDR standard - Dolby Vision is supported by these receivers.
The Denon AVR-X3500H has 8/3 HDMI inputs/outputs versus 7/1 HDMI connectors of the Marantz NR1509. 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. These compared receivers have a built-in phono stage for connecting a vinyl player. Supported voice control technologies are identical - Amazon Alexa, Google Assistant, Siri, Josh.AI. It is also worth noting that the ECO mode is presented in each of the receivers. Both AVR-X3500H and NR1509 can be configured using the Setup assistant.
Only the AVR-X3500H has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the AVR-X3500H.