Read: they are soft. 
I can see the point as getting a cheap but hopefully good lens, and also maybe challenging oneself by going full native, I mean, manual. In that case I would've gone for the Nikon, maybe the Olympus, but not the other two.
I can see the point as getting a cheap but hopefully good lens, and also maybe challenging oneself by going full native, I mean, manual. In that case I would've gone for the Nikon, maybe the Olympus, but not the other two.