The best thing about digital copies is that you can take that and give it to a friend to play as well. Or perhaps the added value of taking that digital copy and bringing it to a store and selling it back to them in case you dont like the game. (sarcasm)
The biggest difference that I see between digital and physical is that you don't actually own the copy of the game when you buy it digitally. Legally speaking, you only own the right to download a copy of the game. In essence, your digital copy holds no value after purchase (other than the opportunity to play the game).