I prefer ebooks for subjects I'll probably only read once and never look at again. They don't take up space, the ereader is lighter, and I can download a book instantly without having to go to the library or wait for a delivery.
That said, I still prefer physical books for reference material. For instance, I still have about 20 books on construction, woodworking, plumbing, electrical, etc. I may grab two or three of these at once and have them open at the same time if I'm preparing to work on a project. Even though I already know most of the subject matter, it's nice to get a little refresher before starting work.
Of course, these days I'm probably more likely to look for a youtube video when I want to do something new.