There´s some good points in this thread. Generally i think photographers jump too quickly to simple conclusions on the subject. A given combination of lens/body/film (or sensor) will output different results between different photographers because the combination reacts differently within various light conditions. All optical constructions have their own unique signature which needs to be learned. In the digital era things have a tendency to drown in mathematical charts and tests. Some Carl - Zeiss lenses are known for their "3D" rendition of light. I suspect this cannot be measured and analyzed although its certainly real (albeit subjective). In my personal experience its all about the optical signature of a specific lens and how it fits each and every photographers unique style.

Also, like polyglot says, large negatives is key!