Sure:
Easy and fast switching between games
Instant sorting and searching
Never lose a game to fire, theft, or borrowing
Easier sharing between rooms, just log in. (This is a big one in a house with multiple consoles, not just sharing with others)
Storage space. I own hundreds of games across multiple platforms, this would be a serious issue at this point.
When you combine that with, for me at least, almost no downside, it's an easy choice. I don't sell games, and I find that where I live 98 times out of a hundred digital games are on sale at the same price as physical. (Sometimes physical is cheaper, sometimes the digital sale is cheaper)
I do miss the whole collectibility part with the box and all, but it's ok.