I like SE very much. Especially because of its details and because I can build and design functional ships and stations. Currently I am building a big spaceport with a functional hotel, hangars, lounges and also an industrial part in the station, where you can trade with things and produce goods. Everything really detailed, also and especially from inside the station.
As you can perhaps see, I'm more interested in building things in detail that you can really interact with in the end and that will work as expected. That includes being able to move around inside a ship or station, use elevators, etc. If I understood the demo correctly, it doesn't exist in Avorion to that extent. So I don't create a room for the crew or a bridge in detail, but I just put a block on the ship as crew quarters and that's it. So I'm afraid I have little influence on how a ship or station works or where I can improve and optimize something.
On the other hand, in SE I am simply missing something "life". In the end everything is finished and works but nobody can use it. There are no outsiders and use the station for trade and barter, at most I have to defend myself against pirates or other factions. But peaceful trade with NPC or other players does not take place. Especially the latter I would wish for.
What I also noticed: At first sight the game looks somewhat "old-fashioned". SE on the other hand looks more "polished" and a bit nicer. There are really nice textures that differ, and a lot of details on the blocks (no matter if from the texture or the 3D model). Somehow most of the blocks in Avorion look pretty much the same. The only difference between an engine block and a hull block, at least in the demo, is that the engine block has a yellow light on one side. Please don't take this as an accusation, these are just things I noticed. Maybe it's different in the full game or I just used the wrong blocks. If so, that would be great of course.