The Contax has a top reputation (except maybe the bokeh). On my Df, the Zeiss Milvus 50/2 earns top marks (incl. for bokeh). Nevertheless, I found the 50/2 AI to have a special (vintage ?) "character", very different from the Zeiss, that makes me use it quite often. Hard to tell why.
I also think that blind tests could lead to surprizing results. As an active (albeit amateur) photographer, my lens appreciation has lots to do with the size, shape, touch, focussing action, etc., so I'm sure to pay attention to other things than the final result, which is not even final (post-processing...).
The only optical defects that I think are difficult to "appreciate" are fringes (esp. LoCA) and mush in the center, and more seldom coma or heavy distortion. Everything else can pass as a virtue in expert hands, depending on the subject... so "optical perfection" remains subjective and may depend on circumstances. The Noct Nikkor is such an imperfect, but beautiful lens. Of course, some lenses (Zeiss 50/2, Nikkor 105/2.5...) will more *consistently* deliver fine pics; maybe that defines 'optical perfection'.
