http://revach.net/article.php?id=3078

Section: Parshas HaShavua   Category: Rashi
Parshas Vayeitzei: Rochel Catches Up To Leah, Mitzvawise
After Bilha gives birth to her second child on Rochel's behalf, Rochel names him Naftoli.  Rashi explains that the word Naftoli means, I begged and pleaded that I can be equal to my sister, Leah.  How can Rashi say that Rochel claimed to be equal to Leah, when Leah had four sons and she only had two?

The Be'er BaSadeh answers that Rochel was not referring to the numbers.  Rochel wanted to have children for her husband Yaakov to fulfill his mitzva of Piru U'Rivu through her, his main wife.  The Mishna in Yevamos tells us that according to Bais Shammai the mitzva requires two sons.  According to him both Leah and Rochel bore the requisite amount of sons for the mitzva.  Bais Hillel says that you must have one son and one daughter.  According to him they were both short one daughter, since Dina was not yet born.

In the language of tzaddikim they were both equal in their pursuit of Tzivui Hashem!