I’m an openhab user since 12 years now and I never regretted.
My personal opinion is that the development of openhab is a little bit slower or more conservative. Means the release cycles a slower and sometimes it took more time until something new is getting into the core system.
The benefit is that it is more stable.
But the biggest advantage is the rule system where you have full control about nearly everything. I’m using python to react to events, cron triggers, thing state changes etc.
My assessment, after reading a lot, is that the home assistant is sufficient for simple smart home setups with around 100 items and a handful of technologies. You can also quickly achieve satisfactory results. But if you work with thousands of items and want to implement sophisticated automation rules, you can’t ignore Openhab.
To give an impression about what I’m talking… My Setup has 886 Items, 95 Things and 10.743 lines of python based rules.
Conclusion from my side, Home Assistant is for beginners and simple setups. Openhab is more for experienced users and more complex setups which requires some kind of clean and well structured core system. So if you plan to fully automate your house and go for it during the next 10-20 years, you should definitive start with openhab.