Took out my red ones and did a visual compare. Even counted the holes in the mesh and I can't see any difference between 2 and 3. Only the small rubber rectangles that are on the front of the toes on 2 is replaced with some other rubber protection thingy on 3. I have lost some rectangles on mine so thats probably an improvment.
Mizuno homepage says the same weight (295 g) and the same rubber compounds.
So it seems to be more or less the same shoe!