It's not really a big deal for me either way. That said, I prefer real books, partly because it's easier to flip through pages. E-books are usually cheaper and easier to get, though, so I typically end up using them.
I prefer a physical book, as with most things. I want to be able to display things in my bookcase, afterall. E-readers or digital copies of books are ok if I'm on the go, so I'm not saying there isn't a place for them.
E-books only for the convenience. While not as satisfying as a large physical collection, I like being able to keep hundreds of books in my pocket via my Kindle. It's nice not being limited to whichever one physical book I slip in my back pocket during the day.
Physical books for sure! Nothing beats flipping the pages through the world of imagination, though there are certain books that I really want but that might be very difficult to get a physical copy of from where I live, so I have to resort to e-books in that case.