# Pyth, <s>12</s> 9 bytes

[Try it][1]

    [email protected]/d

Saved 3 bytes thanks to Mr. Xcoder.

### Explanation

    [email protected]/d
        m  /d   Count the occurrences of each element.
         .m     Take only those that appear the minimum number of times.
      @F        Apply the above to A and B and take the intersection.
    eS          Take the largest.

  [1]: https://pyth.herokuapp.com/?code=eS%40Fm.m%2Fd&input=[1%2C+3%2C+4%2C+6%2C+6%2C+9]%2C+[8%2C+7%2C+6%2C+3%2C+4%2C+3]&debug=0