Shenzhen I/O is an improved TIS-100. The story is much more worked on, and also has the solitaire aame extra (it's fantastic).

Also, to some extent, Shenzhen I/O = TIS-100 + SpaceChem

I'd say TIS-100 is the better game. But I think that's just because it favors a style of optimization that I really enjoy. Ultimately that's what I think it will come down to.

TIS-100 felt more like building some interconnected pipeline but Shenzhen feels more microcontroller-y

It's a very polished (graphics, UI, story) and expanded (many more chip types) sequel.