I used to track my cars (too old now) and going in and out of tires you were very aware of big differences. How much this makes a difference at normal road speeds is a question of degree. In most controlled tests, wet stopping differentials are usual within 3% over tires of a similar calibre. That said, tread depth and tire temp has far more impact on objective driving characteristics than did brand. The only exception was tendency to hydroplane (large differences- some tires you knew did not perform in standing water) and behavior at the limit- some tires just give you that much more information before letting go. I guess if you are pushing your MOG to the limit, it's useful to find the best tire. As I just like to cruise at a reasonable pace, not a biggie so long as they keep their cool when it rains.
