But there is data. We can debate how reliable the various data points are, but you really can't deny that ICV2 rankings or Amazon rankings or even anecdotal stories are data. Sure, they all have different degrees of accuracy and none represent perfect information, but they are all still data.
Another available point of data is one company flat out stating that their sales are higher. Again, not perfect information, same sort of things can be discussed (how do they know, are they mistaken, how long will they, release cycle, yadda yadda yadda).