Digital offers no advantage other than no disc swapping but I am not that lazy that I can't get up and switch discs.
Retail offers:
-Physical Game and Case
-Possible Physical Goodies (Maps, Reversible Covers, etc)
-Ability to share the game with a friend easily
-Ability to sell or trade the game easily
PSN, XBL and the eShop rarely ever have games on sale for a cheaper price than retail, and when you add GCU and Prime discounts its even more rare.
I see no reason for digital...at all. This thread is a great example.