When coming to books, I prefer paperbacks rather than ebooks, but If the price of paperback is much more than ebook, I go with ebooks.
I have almost stopped buying books other than textbooks from offline stores as online stores almost always beat them in price.
I check price on Flipkart, Amazon and Kindle. If kindle proves to be more than 100 rupees cheaper, I go with it. Otherwise, it's the cheaper one between flipkart and amazon.
Recently, I have heard about a site cAllen Bookchor which is gaining immense popularity. It sells read books at amazing bargain.