I've read the PoP journals many times on Kindle, and it looks great. Can't speak to the Karateka journal, but I imagine it's not far off.
I don't have the physical one, but I can't imagine what I could be missing out. If anything, you can keep reading it on your phone if you don't have your e-book with you etc.
Sometimes books with diagrams, pictures, source code, look bad on an e-book.