Luckily, most of them come with tone control knobs. Doing a comparison of a bunch of different basses all set flat is slightly useful, but not very. Doing a comparison of a bunch of basses where they are each set to the ideal tone control settings for the style being played, now that is a far more useful comparison. I suspect with that type of test, they might not be so drastically different from each other.
Of course the longest scale is always going to win on the B string. That is called physics, and the laws of physics are fairly tough to overcome.