Interesting review. Chris Niccolls from PetaPixel was actually quite positive about that lens. Looking through the reviews I can see why either of you arrived at the conclusion you arrived at.
Looking through the old reviews on this site, I discovered the 50 f/1.8. It seems both lenses have almost identical MTF figures at the shared aperture values. For example both require stopping down to 4.0 to give an even MTF performance over the full frame. Given what I wrote in another location, that a fast aperture on a mirror less body looses it's edge when it comes to finder brightness, going for the f/1.8 lens will save you same weight, space in your bag and money over the f/1.2 version.
The 45mm is wider than the 50mm, that is a differentiator.
