When KSP 1 shipped its alpha, there wasn’t a perfectly functional KSP 0 it was competing against. From what I’ve heard, they’re using the KSP 1 engine (restricting how much better they can make things) but are somehow shipping with many of the KSP 1 features missing. So it’s kind of a Worst Of Both Worlds situation.

Until KSP 2 achieves feature parity with KSP 1, I don’t see any reason why I should buy it.