Hardcovers are perfect for games you really, truly love. They make fantastic shelf display items and they make holding them feel pretty cool. I only have a few hardcover books but that's cause ordering online is tricky here in Manila. I lost around three hard cover books that supposedly got shipped to this country but even reached me. (Who knew someone would steal rpg books!)
Softcovers so far are the easier to reach tier when it comes to releasing my own stuff. It definitely is nice to have something physical to hold when you order something, or when you release something for others to enjoy.
Digital is economical, helpful, and with dwindling eye-sight vital to maintain the hobby. It allows for easy transport and for simple bookmarking. But while it serves utility very well, there's something about having the actual books that makes the whole thing feel worth it.