I prefer digital books because of the following points:

• There is a book price control in Germany, meaning that you can’t get new physical books cheaper. This does not apply to digital books.
• They take less physical space.
• I can read them everywhere with either my Smartphone that I already have with me at all times or my tablet. I do not have to plan to read a book when I’m on the go.
• I can quickly search for something in a reference book if I have it in digital form. This is not possible with physical books.

Only downside:

• I need to have a device when I want to read a digital book. And this needs to be charged. But this is rarely a problem.