Shootout: Canon 5DS R vs Canon 5DS vs Canon 5D Mark III vs Nikon D810 (Old Map)
Get Canon 5DS and Canon 5DS R at B&H Photo.
This 4-way shootout shows a number of useful things.
Sharpness: 5DS R vs 5DS vs 5D Mark III vs Nikon D810 (Old Map)
With a very large actual pixels crop for all, plus multipel crops with all cameras sampled up for easy comparison. The differences are plain to see and useful to understand.