Who chooses?

I remember one day in grade school standing in the cafeteria line for lunch arguing with a schoolmate.
She insisted that Crest was the best toothpaste. That’s what her family used.
I insisted that Colgate was best. That’s what my family used.
In my heart I believed that whatever my parents chose for us was the best there was.
Is there a “best”?
What is “best”?
Who chooses?
At 75, though I have used other toothpastes, I still use Colgate.