I do not know much about coating. But having used Rollei for many years I still love the look of the HFT coating most, as most of them are reddish brown or reddish purple. I do not like the greenish look of the Contax ones. Also for B+W and Heliopan filters they are almost all the time reddish/purpleish whereas the Hoya ones are clearly greenish. But the made in Germany Zeiss lenses of the Contax and the Rolleilflex seems to have the same greenish tone, like the 60/2.8, 16/2.8 and the 18/4.
_________________
Rolleiflex 3003, SL2000F - SONY Alpha7R 1/2/4. A1
Carl Zeiss C/Y T* - QBM HFT - ZM T* - ZF T* - Batis T* - Otus T* - Loxia T*
Sony. Zeiss 16-35/4 T* G200600 GM100400 GM600
http://www.fuwen.net