Smlight SLZB-MR5U vs Sonoff Dongle Max

They are very close. The Smlight SLZB-MR5U wins on features with a fully supported dual-network mode and a Bluetooth proxy, while the Sonoff Dongle Max is cheaper and better reviewed. Both are network-connected EFR32MG24 Zigbee and Thread coordinators.

Dual network and Bluetooth. The Smlight SLZB-MR5U runs Zigbee and Thread simultaneously as a supported feature and adds a Bluetooth proxy, whereas the Sonoff Dongle Max marks its dual-network mode experimental and has no Bluetooth proxy.

Yes. Both the Smlight SLZB-MR5U and the Sonoff Dongle Max connect over USB, Ethernet, Wi-Fi and PoE, so either can be mounted away from the host machine to cover dead zones. Both also use two external antennas rated +5dBi.

Yes, both run the Silicon Labs EFR32MG24 as a Zigbee 3.0 coordinator and Thread border router, and neither supports Z-Wave. The practical split comes down to the SLZB-MR5U's supported dual-network mode and Bluetooth proxy versus the Dongle Max's lower price.

Buy the Smlight SLZB-MR5U if you want reliable simultaneous Zigbee and Thread operation plus a Bluetooth proxy in a network-connected coordinator, and you value those features over saving money on an otherwise similar stick.

Buy the Sonoff Dongle Max if you want most of the same flexibility, USB, Ethernet, Wi-Fi and PoE placement with strong twin antennas, at a lower price, and you can live with an experimental dual-network mode and no Bluetooth proxy.