While the best motion sensor topic has been inactive, I wanted to add my initial thoughts on the Sonoff versus Philips Hue motion sensors by way of comparison, for other newbies like me who are just researching the topic and really don't even understand what considerations makes one sensor "better." At this point, I have only had experience with these two Zigbee motion sensors (though I have a HomeSeer HSM200 zwave on the way to test, because it doesn't need batteries ).
Sonoff is significantly cheaper.
Both sensors were found with Hubitat, but the Sonoff need to be close to the hub, while the Philips paired from another room.
Sonoff takes a CR2450 coin battery, while the Philips takes two regular AAA (if I remember right). Sonoff requires you to pry off a plastic piece with a screwdriver which: (1) is likely to break at some point; and (2) is a pain once the sensor is mounted with sticky tape. Phillips has a screw held backing.
Sonoff is about 1 in x 1 in x 0.5 in. Philips is about twice the size. Sonoff sensor has a dimpled "golf ball" look, while the Philips has a smaller, and in my opinions better looking, dome. Here's a picture for comparison.
Sonoff is just a motion sensor, while Philips has motion and temperature and luminance. The Philips temperature seems right on in comparison to my other thermometers. I do not see any lux reporting right now on Philips, but, as I'm not using that feature, I haven't debugged this to see what is going on.
Both motion sensors are very responsive (as good as the famous Lutron Caseta Sensors that I also use). I cannot speak to range, the application was only about 10 feet away.
Sonoff will give a little flash of reddish-orange when it detects motion. Philips has no distracting visual indication.
Sonoff only gives double sided sticky tape to mount. This means—unless you rig something up—you can only mount flat to a wall. By contrast, the Philips has a clever magnetic mount that allows you to angle the sensor, and easily take the sensor down to replace the battery. Both are rectangular cuboids, so you can simply place them on a shelf.
Philips has a settable cool down period after sensing, and looks to default to 10 seconds. Sonoff is fixed at 1 minute. This is a big deal. If you walk in a room, then manually turn the lights off, then return in 11 to 59 seconds, the Sonoff will not turn the light back on, while the Philips will. If you never manually turn the lights off, you may be able to get more battery life by setting the Philips to have a higher (up to 30 minutes) cool down.
Conclusion: If you want a cheap and fast motion sensor, and do not care about aesthetics, fast cool down, or maintainability go with the Sonoff. If these features are important to you, and you can pay the price, go with Philips.
2020.09.18 Edit: Having had both sets of sensors up for about a week, I am experiencing false motion detections with the SonOff. This is a deal breaker for me, as I do not want my lights going on randomly or not shutting off after the inactivity time.