lic4
Well-known
Haven't used the 28 Rokkor, but the 28 M-Hex is quite a bit better than the Zeiss 28. The M-Hex is a clone of the 8 element Elmarit V4, and sharper than a Summicron 28/2. The build quality of the 28 M-Hex is miles above any CV or Zeiss lens.
I can't say this is accurate scientifically, but I had the same results between my Hex and my Cron 28 - the Hex had sharper edge to edge images in general use. I haven't tested using lens charts or brick walls though, just based on a few images and enlargements to 11x14