Choosing between a powerful student who would protect the village at all costs, even at the expense of what's right versus a powerful student with a strong will of fire, there was really no chance for Danzo.
If he had to make a second choice, Tobirama would probably even have chosen Kagami or Koharu or that Akimichi kid or fodder over Danzo... and this is a parallel that needs to be drawn with Naruto and Sasuke that is what ultimately sinks Sasuke's chances of becoming Hokage,even if his policy of protecting Konoha is completely sincere