He has won a higher percentage of headed duals than Bartra by those stats.
By your reckoning someone who tried to win 10 headers and makes 4 gets more praise than someone who tries to win 5 headers and makes 3.
Masch is not better than Bartra in air but Pique is.
That bolded part sums it up, really. Pique is by far the best player we have in the air, with Bartra being the only other player we have that can even be considered an aerial threat.
Bartra throws his head in there more than a lot of other players but that's more down to attitude than ability.