With Space Engineers getting its planets this week, its going to be hard for Empyrion to keep up. I backed Emp in KS (not reached), stage. Then pre alpha access. Its a good game and could beat Space Engineers in the survival department. However, now with the new planets arriving in SE, and the fact that SE is completely open, with hundreds of years (our years) worth of space to explore (without loading screens of any type), it is going to be a challenge for Empyrion to keep up, even with the survival aspect. They're are also rumours of more survival things to be added to SE, plus of course the Sabroids (space spiders), as foe, it just gets better and better.
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Now Space Engineers does have its problems, at the moment there are issues with DX11, plus other bugs. But as many of these games are, its in early access still, so beware the buyer, as always. For me Space Engineers wins out over Empyrion, but its great to have the two similar games, that way they keep each other fresh, at least for a while.
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Space Engineers is quietly one of the best space sandboxes available. But Empyrion is building and has only really recently started, when compared to SE. So it could all change later.
I think its just nice to have all these games available in the genre.