both lenses are excellent, but if i had to choose I'd take the Xenar -- the one on my Rolleicord does lovely things to whites.
The Optar is a more generic lens, as I understand it, aimed at the professional press market (as was the Graphic) and will do you good service, but it won't have that glow the xenar will. Also hard to beat a good working compur shutter.
Thank you...This is the type of answer I was hoping for. Very helpful. Thank you.