The only constant variable between those games is the voxel, which when boiled down to its base form, is really good simply for building stuff. Regardless of genre. I'm a community moderator for Blockade Runner though, so I'm partial to BR's set up, but I've played Cornernoids and the -old- demo of Scrumbleship before.
All three games are interest in the same thing, creating semi-realistic spacehips, fighting, and large multiplayer components. But in my experience, Blockade Runner's is going to be more of a Dwarf Fortress fan's wet dream. It'll have real complexity, making choices actually matter; designs that require actual thought on how power distrubition, gas and fluid dynamics work in space. Not to mention the crafting system, which will NOT be like MC's or even Cornernoids; and will probably end up being very detailed and massively complex.
At the moment, there's not much else known about Cornernoids than what has already been released. It already has gameplay features, but nothing innovative, and nothing polished beyond the basics of movement and flight controls. I'm almost afraid that Cornernoids is going to run into the same problems MineCraft did by rushing in 'game' features without working on the backend programming first.
Scrumbleships, on the other hand, has been in development for almost as long as Blockade Runner has been, and until recently has been really hush-hush on its developement. Point of fact, Scrumbleships' creator used to stop by the BR IRC channel every so often to talk shop and to spread the word. Other than that, I cannot say. All you used to be able to do was to select a block type and place it. I don't know how far its progressed now.
I hope this answered some of yoru questions, Deus Vult.