I voted ebook but it's not so clear cut in reality. I have a preference for ebooks because they take up less space, both in terms of storage and because I can just slip my Kindle in my bag when I go to work or out-and-about. If I've forgotten my Kindle, I use my iPhone Kindle app but it's not ideal. Still, it's fine if I'm on the metro or in a waiting room and need to pass the time somehow.
Real books are still a pleasure. I prefer academic books to be physical. It's just easier to look through quickly. If I get given a physical book, I'm happy to keep it and read it.
But for preference, I will always choose the ebook version.