This is just an afterthought, but the 58mm lenses were no longer in production when Minolta began the Rokkor-X designation. The lens designers had moved on to 50mm as the "new normal" focal length and left the 58mm formula in the drawer. Bummer, bc it is a *great* focal length for portraiture.... For my consumption, the Rokkor 58mm f1.4 is my go-to b&w portrait lens - what's Leica got on it? Nuthin. ;-)
Otherwise, the MC Rokkor(and -X variant) PG 50mm f1.4 is really sharp and my choice for "normal" focal length use for color photography. I have the MD Rokkor-X 50mm f1.4 and it is missing something - probably my perspective only. I've read other well-experienced Rokkor users extol the virtures of the MC Rokkor-X 50mm f1.7 being sharper than the f1.4, but i'd have to see some negs or really large prints under loupe for proof.
I would agree that the 58mm f1.4 lens is better for portraiture than the later 50mm f1.4 lenses, but IMHO, the 50mm lenses are superior for everything else. However, I could see the argument that the 58mm lens makes a better compliment to the 45mm f2 than does the 50mm. But, if you actually plan on using the lens at f1.4, the 50mm lens is sharper and contrastier than the 58mm at f1.4 - however, those advantages might be disadvantages for portraiture.
I actually got the best of both worlds. I found a 58mm f1.4 lens that has a busted diaphragm, so it is only useable wide open - or as a loupe. That lens cost me $2.