I have tried both but I’m a mere electronics engineer - not a programmer and I find HA less daunting than OH. The people at OH seem to be heading in a very precise way based on ideology and standards whereas HA seems to be more tolerant of the enthusiast approach. I feel the OH one maybe the right way but not the successful one.
Having said that both seem very stringent on how addons get approved and meeting quality standards, which is comforting. Both are producing great releases.
I like the impetus with HA releases but it seems they are not as stringently tested to be robust, but I can work with that. They are usually fixed within a day or so. I also feel I can ask questions in the HA forums and bar a few ‘characters’ you can expect to get a helpful response. With OH I expect to be belittled , or provided with only sparse information.
So I’m quite happy with HA at the moment and the recent visual developments for the UI options are great. It’s doing what I need (mostly) . OH has some ambitious plans to address the UI too with a replacement to Paper UI but they seem to be the trailing runners in this.
OH have also just announced they are merging their commercial offshoot (the ‘open standard’ Eclipse commercial project foundation) back into the OH umbrella - which I think is a good move for the future but to me indicates they can’t get long term commercial developer commitment to Eclipse . Deutsche Telecom are pulling out it seems.
So I’m passingly with both but focussing at the moment on Home Assistant.
(BTW I also like HomeSeer.)