I have been using (samsung) SmartThings - but not great. I have just been too lazy to switch so far.
Vera has a good reputation as far as I know
Homey is the most flexible but has stupid voice control system :
https://www.athom.com/en/I use SmartThings mainly for light switching and to switch things off (and sometimes on)
My toilet with no windows - is light and fan automated.
Our TV room switch off all TV/Games stuff at midnight to save the 22-30w standby
I have alerts if doors open and we are not at home or if an entry door is open > x minutes.
I have a few "mozzie" sprays that turn on automatically at night and switch off 1am' ish when we are present.
Issues with all the systems:
1. Firmware updates - mostly no standards - so if sensors & control device is not from same company - PAIN
2. Quality of sensors - many sensors are made from "new" companies who have never designed plastics before. So for SmartThings it means most battery holders break / become brittle after 2-3 years. Double sticky tape will not hold sensors in place for long (Fibaro, SmartThings) so use the screws.
3. 3rd party sensor support - SmartThings supports a range of 3rd party sensors either via SmartThings developed or user contributed "plug ins" - Vera - I don't know - Homey - seems like a lot of 3rd party development (more than SmartThings) - each system have its own ups and downs. SmartThings are usually only implement a subset of features. So my advice - find the sensors you need FIRST - then select system from that.
4. There are lot of systems on 800/900 MHz (868 in EU) MHz but there is also a lot on 433. My next system will support both (at least - for both Zigbee and Z-Wave & 433). SmartThings does not support 433 - so no reading of Oregon Weather station data etc or turn on/off the very cheap 433 MHz plugs. Homey is supposed to support them all. Vera can with 3rd party 433 MHz gateway (as far as I remember)
5. Many sensors have terrible battery life. Take out a subscription on Amazon for the batteries you will change every X months.
- so I prefer mains wired.
6. Official Integrations - SmartThings does officially connect to Netatmo and other fun things. But bug's can take ages (we are talking YEAR(s)) to fix.
7. No provisions on ANY of the systems to hand system control over to fx a tenant or new owner - either permanent or temporary.
8. Many things in SmartThings relies on Internet connection. So some automation's will not run if internet is down.
9. Some sensors are very slow to respond or gateway is slow to pick up - so fx Toilet light automation works best with SmartThings own presence sensor. Else we could stand for 5-10 seconds in a dark toilet....
i have probably forgotten a lot of issues
IMHO It is not ready for prime time anytime soon....