You still could set up a study where you have tasks that users must complete and you get countable results. But this would quickly get expensive, so you need a sponsor. This could either be Apple, Google, or some other company in the market interested in making their opponent look bad. And I wouldn't take such a study for granted.
Not only expensive but making a comprehensive one that people actually finish is practically impossible.
And there are many many further aspects that make the measurement non-reproducible - and so unreliable - or biased.
Right. Like I said, the only parties interested in taking all that effort and that have enough money are probably Apple, Google or maybe Samsung. Independent companies won't go down that hole.
