Having had an opportunity to test Pioneer VSX-531 vs Pioneer VSX-933, I’d like to share my impression here to facilitate your choice of a new AV receiver.
The number of channels for receivers is different - 5.1 versus 7.2, respectively, for devices. In terms of power, there are differences, the VSX-531 has such a ratio W/Ohm - 80/8 20Hz-20KHz, 140/6 1KHz, while the VSX-933 has a power of 80/8 20Hz-20KHz, 165/6 1KHz. A common feature for devices is the same total harmonic distortion - 0.08%.
The manufacturer installed different DACs, the VSX-531 received the model 192 KHz/24-bit, but the VSX-933 is equipped with AK4458 384 KHz/32-bit. The Bi-amping function is implemented only in the Pioneer VSX-933. Both Pioneer VSX-531 and Pioneer VSX-933 can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Each of the receivers has a Bluetooth connector. The VSX-933 has access to the Spotify service. The quality of 4K 60p signal remains unchanged when transmitting from a source to a TV or projector via HDMI for both receivers. Signaling over HDMI in standby mode can provide the VSX-531 and the VSX-933. Video scaling is only possible with the VSX-933. Operation with the Dolby Vision is only possible with the VSX-933.
The number of HDMI inputs/outputs varies depending on the receiver, the VSX-531 has 4/1, and the VSX-933 has 6/1. HDMI Audio Return Channel is implemented in both devices. HDMI eARC is not supported by the VSX-531 and the VSX-933. When comparing receivers, it becomes clear that each of the rivals can work with HDMI CEC. VSX-531 and VSX-933 support the standard HDCP 2.2. In the presence of a built-in phono stage for connecting a vinyl player only at Pioneer VSX-933. There is an ECO mode in VSX-531. The Pioneer VSX-933 can be properly configured using the setup assistant.
A Dolby Atmos multichannel audio format is available only in the VSX-933. Only in the VSX-933 realized a DTS:X surround technology.
The Pioneer VSX-933 is better receiver in this comparison. Check Pioneer VSX-933 price