There's no quantifiable way to measure who has a better flick. In fact, the quality of most other mechanics can't be measured . Every pro has crazy clips and embarrassing moments on LAN and one stream.
Any meaningful debate or argument that tries to be initiated and replied to by a subjective opinion like "Oh, but Aspas' flicks clear J0nggg's flicks" or "Oh, but Aspas has better reaction time than S0mething" is stupid. Only debates like "who is the better oper" hold slightly more weight because stats can be provided. But even then, it's not always easy to compare as so many factors come into play, such as consistency of the oper, the maps, which teams were playing and how good the teams were at that stage, the time of the year, etc.
I rarely see these conversations, though, simply because they take much more effort to compile the data for such a stupid conversation that people won't appreciate.