You can expand the blurred image components into a series, with the coefficients being objective parameters that specify the bokeh as precisely as you like it.
No, that's by no means clear. If A resolves 100 lpm in the center, but only 80 in the corner, whereas B resolves 90 lpm throughout the image circle, it depends on the application. A lens with 100 lpm that distorts like a fisheye is really bad at repro photography, compared to one with only 80 lpm but negligible distortion. The MTF function depends also on the distance the lens is focused at. Things are not that easy ...
Of course there is. If you compare e.g. "CZ lenses" to "Japanese lenses", you're comparing entire populations of lenses. Unless there are certain features that correlate with "CZ" or "Japanese" to a statistically significant extent, you cannot make blanket statements about certain brands.
Actually, this would be necessary, since consistency/quality control is also a performance metric when making blanket statements about lenses of certain origin.
Which makes these numbers meaningless, since we photograph with real lenses, including their manufacturing tolerances, not with computer simulations.
If you trust the manufacturer that they publish typical data (i.e. one based on statistical analysis of the influence of the manufacturing tolerances), not the "best case" data. Ideally, they should also publish the "worst case" data. You find this information in the data sheets of components that cost only pennies, but I have yet to see it for photographic lenses that cost thousands of dollars.
