It seems that with this game, the building block allow for an infinite amount of creative use, not only to solve the puzzles, but to build machines that are more clever and efficient than anyone else. I've seen videos of people making computers that can count, display a clock, and even generate cellular automata using solely the mechanics of the game. While I can't speak to the draw from the Spacechem geniuses out there, I've seen videos of people that make insane contraptions in Infinifactory to be as efficient as possible. Infinifactory, on the other hand, makes it much easier to get a dirty solution to work, and to me, getting ANY solution to work for many of its later puzzles felt like an intellectual triumph. I played Spacechem and found it nearly impossible for my intellect about half way through. This does NOT make it less sophisticated than Spacechem.
However, while Spacechem was very limited on space, Infinifactory, including its "inside" levels, has much more room to come up with dirty solutions. this is the ultimate puzzle game! Like many have noted, this is very similar to Spacechem in 3D.