The only advantage if you are using HA is that the Harmony integration comes with many predefined controls. If you have “activities” set up, then they work in HA too which is nice.
Compared to something like a Broadlink, there is more work to get the BL set up, but once you have it set the functionality is basically the same (in HA).
In terms of offline use, I’m not sure. I would be surprised if they just bricked all of these devices over night, but you never know. There is a login that obviously uses the Internet, but I don’t think that regular use goes through the cloud, so they should still work.
Like I said, if your primary use is with HA then you have many other good options.