Certainly individual copies will show variances due to age and environment.
My favorite OM Zuiko 50/1.8's are the silver nosed F.Zuiko and the first gen black nosed MC. The acclaimed MIJ and 'Japan' marked versions have sealed front groups that can not be cleaned. If they have internal haze or fungus you have to live with it.
Although tie 1.8's are reported to be sharper or more contrasty, I prefer the 1.4's especially for their 8 aperture blades versus 6 on the 1.8's.
I would like to add that my experience with OM lenses is they all benefit tremendously from the use of a lens hood in daylight.