Most definitely digital. I really don't see any advantage of physical books over digital, besides that some look pretty.

I can read in bed without having a bright light, I can lie in bed and don't strain my hand to keep the page open, I can modify font/font size/spacing, I can buy a digital book and read it right away, I can take thousands of pages with me on vacation and only need the space of a small brochure, I can real-time translate words I don't know.

Just overall the better experience for me.