I started my home automation journey with Smartthings. Moved to Hubitat and finally landed here on Home Assistant.
Smartthings -> Hubitat was brought on from all the cloud outages of smartthings and the delays the cloud introduced. I wanted local control for better reliability. Seeing the changes ST is making right now, I’m quite happy I moved away from the platform. Even after the switch, I kept some devices on Smartthings that just don’t work well with Hubitat (Schlage locks, Daikin AC) and used hubconnect to integrate them into Hubitat.
Hubitat has really great and stable radios. They’re first to market with a 700series z-wave chip and their zigbee radio is rock solid. Where Hubitat is weak I find is the processing power. If you’re doing more than a couple basic automations, you’re going to start experiencing slow downs. And I’m talking to the point where things can take minutes to respond. There’s even apps developped to automatically reboot the hub on a daily basis. Most “power users” have stopped using the built-in Rule Machine (which is clunky and painful to use) in favor of offloading all logic to another platform. Node-Red on a pi has become extremely popular. As for the smartphone app, it’s terrible. Slow to load and painful to use. They make an attempt at built-in dashboards but they’re really not good looking. Nothing compared to what can be done in lovelace.
Home Assistant for me has been extremely solid. I’ve still got Hubitat in the mix for its radios and am bringing them into HA through the Hubitat custom integration. To me this has been the best setup yet. No more hub slow downs, full local control, integrations that I’ve never been able to get on other platforms. Plus I can run on my own hardware so I don’t have to worry about processing power limitations. I would recommend Home Assistant over the other 2, even though it’s a bit steeper of a learning curve. And if you’re just starting out, I’d seriously look at using a Hubitat hub for the radios over a Zigbee and Zwave USB stick.