Xiaomi/Honeywell Smoke Detector
If we look at Zigbee smoke detectors, there are not that many well-known brands that make them. You have the Friend Smoke Detector and the HEIMAN Zigbee Smoke Detector which are readily available.
If we look at the size of these 3, they are almost all the same size, one is a bit higher, the other a bit lower. If I had to choose anyway, the Friend looks the smallest because of its round shapes.
All 3 detectors give 85db of sound and all have a built-in LED to visually show the alarm.
Are there any differences? Yes, it's in the price. The Heiman and Xiaomi are the cheapest of the 2 because they are for sale for around 30 euros. The Friend is a bit more expensive because it costs about 40 euros.