I've read both books and done the Nand2Tetris course.
I think Code by Petzold is decent in that it's a book you can read in bed etc. but it spends a long time discussing mechanical relays as an analogue and later discusses various processors in depth.
I think Nand2Tetris is slightly better in that it focuses on what I'd consider to be the most important stuff, but it's an actual course and requires significantly more effort.
Nand2Tetris is probably the best course I've ever done though, including my university studies in Physics and ML. It's fun and you learn loads.
I agree somewhat with your assessment of “Code”. I read it first and then “Elements of Computing Systems” and I found reading them in that order was great because the latter puts into practice what the former simply describes.
I think Code by Petzold is decent in that it's a book you can read in bed etc. but it spends a long time discussing mechanical relays as an analogue and later discusses various processors in depth.
I think Nand2Tetris is slightly better in that it focuses on what I'd consider to be the most important stuff, but it's an actual course and requires significantly more effort.
Nand2Tetris is probably the best course I've ever done though, including my university studies in Physics and ML. It's fun and you learn loads.