This is a quick test to show the obvious difference between the 2. For some odd reason, 180° appears much more like a 360° shutter-- as if it were being left wide open. There is substantial motion blur which should not be there.
To make 172.8° look proper, I added Real Smart Motion Blur. Which is a plugin that adds in the appropriate amount of motion blur to simulate what a 180° shutter angle would look like.