How do you apply science (and I am a physician) to measure the quality of say, the Mona Lisa?Art relies very much upon opinion and personal taste, even if it comes from a "stranger".
Well I can give you my opinion, and I'm an engineer.
I think, quality as such can (and should, imo) be broken down into the aspects "technical quality" and "artistic quality". The technical quality can be measured in terms of sharpness, distortion, vignetting, chromatic aberration. So the technical properties of two lenses can very well be compared.
The artistic quality comprises things like choice of sujet, point of view, focal distance, lighting, timing and probably many more. These are indeed harder to quantify and to compare. To an extent, this may be a matter of personal liking. Although I'm sure, experienced photographers would mostly agree on a ranking in terms of artistic value of a given set of pictures.
As this thread is about how lenses compare, this should (again: imo) leave out all artistic and personal aspects.
All artistic aspects being equal, including the photographer himself, I'm sure a technically superior lense would render the better picture. (with "better" having the meaning of "closer to reality").