I know that a lot of people love the Xiaomi motion sensors. I recently retired about 10 of them from my environment. Although they were working well, I decided to move on to Iris as I had some serious mesh issues going on. We wont pull that band-aid off again. Anywho - I just wanted to communicate the differences I've noticed comparatively.
I use a LOT of motion in my environment. I like them to keep the lights on when they need to be and immediately off when they don't. I have sensors in my environment based on my expectations. And my expectations are reasonable. That being said, here are my comparisons.
I have a motion sensor on my desk. Xiaomi kept my lights on about 85% of the time. I had to make sure that I kept moving or my den lights would turn off. This happened maybe once an hour. That, in turn, would turn off my living room lights. Grr. So, now, I have to get up and walk into the living room to trigger them or pull up a dashboard and turn them back on as they stay on because I'm in my office. I don't like the lights to remain on for more than 2 minutes after motion stops. I know that's picky and quite the expectation, but it's what I like. I haven't had any issues with lights turning off after switching to Iris. I have to sensors in my office. One on the wall to monitor my work bench and the other at my desk watching my hands. Working at my bench had been a constant fight to keep lights on. Now, it's not even a concern. Literally.
In my kitchen and dining with the Xiaomi motions, I had to us a button that kept my lights on when we were in there. I have 4 motions and one multisensor 6 to cover the room appropriately. That should be plenty. Then, we had to remember to turn it off when we were done. This goes against my promise to my husband to NOT have to do anything extra to keep a light on. (song and dance, button press) Since moving over to the Iris motions, we haven't used the button once. There are more examples, but those are the big ones since we use those rooms the most and are most noticeable.
My conclusion is that, although the Xiaomis were small, receptive, and mostly reliable, I feel like the Iris sensors have surpassed them in performance. I fee like Iris have better range and would detect a fly itching it's leg at 20 feet. It's just such a noticeable improvement to my environment.
So, If you're considering motion sensors, I'm not discouraging any decision you're making, I'm just sharing my experience. I really liked the Xiaomis. But, I like the Iris motions better. I have 16 iris, 3 aeotec multis, and 2 gocontrol pir motions in off areas.
And I really dont miss the "oh f*&^%g hell" coming from a room when the lights went out due to not picking up movement (from the Mrs). I also tested one where I sat still, whilst watching the logging to see at what point it registered movement, all I did was tilt my head slightly, and that was picked up from the top corner of a wall. Amazing 
Although the postage to Asia may work out too much for my wallet 
