So by your logic, you will judge if Messi is better if and when he scores more goals than Son for Spurs?Was Soldado better than Crouch?
As I pointed out I'll judge if Draxler is better if and when he scores 24 plus goals for Spurs
It's ok to use your judgement based on player performance irrespective of which team they play for. We can absolutely disagree on the ability of a player. You can even point to Draxler playing in the French league as a reason that he might not be as good as he looks. But surely irrespective of players playing for Spurs, they can be judged to be better or not than current Spurs players.