So, the main thing is how building works. Instead of just building assembly lines and scaling them up in size to fit more production, you build space stations that need to balance a few things, like energy, heat, and stability. The building system makes construction of assembly lines a more interesting puzzle than in most games. Furthermore, the more fussy and perfectionist you are, the more interesting it gets, since you can minmax each station and waste very little space.

The other aspect that's pretty unique is logistics and mobile stations. In many factory games, getting resources to your stations is just a bit of a nuisance and involves placing long conveyor lines, and is later replaced by a transport system. Usually trains, with varying levels of complexity in the implementation of rail networks. Final Factory instead has a more flexible system right from the start that lets you get resources to your stations easily, and much faster than having to build conveyor belts. You place drones that move in long linear paths, and can daisy chain them to move material over long distances. In the midgame and onwards you can even make the game's equivalent to trains, mobile stations. You can see how they work in the trailer, they basically are factories that can move to different points in the map on a schedule (with a fair amount of configuration). This is probably the game's most unique feature, and it enables a lot of stuff like having perimeter defense around your factory via massive warships, logistics with freighters that distribute resources to one another in ports, multiplexing, etc.

Follow up to last reply, here's a video from one of the devs explaining the station movement system. Never seen anything like this in other factory games, closest thing is Minecraft Create mobile bases.

https://youtu.be/qzGVDggR6rA