I have to agree and disagree with your statement. Yes, it is true that one's experience in one area doesn't prove much. But you're going to have to realize that not areas are "equal." Some areas are more populated (more customers, more money, higher priority); that's why the abysmal performance by AT&T in such areas are echoed through many mobile forums.
You also can't say, "Oh well Sprint has the same coverage because it's supposed to use the same towers where they have no towers." There is also stuff to take into account such as tower priority, and tower signal quality where there are Sprint and Verizon towers. Why is it some areas have a stronger Sprint signal and some areas have a better Verizon signal? Well in theory that would never be if "they have the same coverage" is the case, right?
I trust real personal experience than "high scientific quantitative 'facts'" in that respect. Because no matter what the "facts" say, certain phones work better in certain areas--in my area Verizon trumps the competition (and yes it is more expensive, thanks again for telling me IOWA because I must have somehow missed that obvious fact due to "blind sheepism" *sarcasm*)
Similarly, if an equation came about and calculated national happiness levels which went against a national survey bent on calculating what people thought their own happiness was... I'd be inclined to believe the survey.