They aren't similar in terms of their physical traits...
Dez is more explosive in the short area but he's also crazy... Dez' craziness will do him in even though he has hall of fame talent. He'll make a fantastic play, but cost his team the game with several other plays.
I would always take a guy like Hill because people like Hill find ways to get better... Character and want-to are two of the most important aspects to a player. Obviously Dez is better right now, but I'd take Hill in the upside department.