Exactly the same as @stefaanv and many others, I started with Domoticz and used it for few years, but after a while it was a bit too much "this script for this", and "this hack for that", and this in python and seven virtual switches for that hack... So I was looking into a more robust solution, and I was sold on presentations that leading people of OpenHAB held online, showing the architecture, the reasons and plans, having clear roadmap and long term plan for the system. I feel I understand how and why openhab works the way it does, why it is organized in such a fashion. And that is very important with any software, to have a good documentation (technical, not just for the users).
With domoticz, almost no idea about how it was internally organized, why and what the future plans are. It was always somehow "well this is what we have, it works, and here are the workarounds... with bunch of hidden difficult to find virtual switches and rest api"
When I started making more "abstracted" rules about events and logic, then lua showed quite a few challenges, but it was mainly having 30-40-50 virtual switches, a pain in the ** keeping track them all, making rules for each of them (f.eks. switches for datetime: isSunrise, isMorning, isAfternoon, isEvening, isNighttime, isDaytime..... isSomeoneHome, isMeHome, isWifeHome,... ) And this was actually the biggest issue I had with domoticz, handling and organizing the automation part and virtual switches. At the end I had like 6-7 times more virtual switches then physical ones.
Then I moved in another apartment and decided to try openhab2. It is just way more robust. It didn't took me a long time to get up and running, and having items defined in a text file is a blessing as you can just do a backup, organize them in multiple files, use git (or backup) for versioning. Writing comments also helps A LOT when you come back to the item after few months/years.
Only thing I was struggling a bit is the RFlink, whose binding is not quite ready yet. But I managed to install and use rflink->mqtt "gateway" and all works as expected.
I am also using node-red for logic as @Fabien which I am still learning, but so far it looks much much better and easier to debug.
Not all challenges from above are domoticz related, some are also "me a rookie" related, so not to downspeak on domoticz, it works great! As long as you are comfortable with all above and dont plan to overgrow it. My goal is to make "smarter home", more then just basic rules and remote home. (about remote home, my.domoticz.com for remote access never actually worked for me, noone could/tried to solve it, so I felt it didn't work)
And that is where the community comes in place, it feels that the people on the openhab are more technical, and generally have great technical discussions about best solutions and approaches. F.eks. only for persisting values, you can have multiple completely different database systems, using the advantage of each of them. And each is very easy to install, as they all comply to some "technical rules and documentation". Now that is a downside, as you need to know that you need persistence strategy at all, I wish some would come predefined, but...
I am not developing anything, but I feel there are "big boys" who think hard about issues and then develop a long term and best solution for the problem. And I want a stable and long term solution for my home automation, and waf
On the other side, openhab is a bit more technical, but I think that someone who can change mysensors sketches and make that work, can make openhab work as well. They are very focused on "non-technical" user these days, and it shows with every update. I guess home-assistant is pushing its way forward.
(a novel about my life and divorce with domoticz will be published someday, snippet above is just the preview, I have too much caffeine cannot sleep help)