I have 3 objects (A, B, C)
Objects A and C are using same texture i.e. Wall.png and object B is using different texture i.e grass.png
Now, drawing objects like this: A->B->C will be inefficient (2 texture changes). To increase performance you will need to sort your objects by texture to have this drawing order A->C->B (1 texture change).
I do not know if the SFML 2.0 is using some internal batching mechanism to minimize device state changes.
I think I will run the test my self.