There's a lot to be said for each, right? I mean, as a collector of books in general, I love having the shelf of hard covers with or without dust jackets that I can look at and enjoy from my chair. On the other hand, moving all of those books periodically is a pain, especially if we're rearranging the living room.
Now, paperback is probably my least favorite of the three. Sure, it's easily portable, but depending on how you port them, they bend, crease, and tear very easily, and ultimately waste away faster.
Digital/ebooks are great for manuals and things I have to flip back through regularly like D&D and other gaming books. I still love the hardcovers though, since at a table they're quickly available if you know where to look for the rule you need.