Which is faster: Map-side join or Reduce-side join? Why?

A.  Both techniques have about the the same performance expectations.
B.  Reduce-side join because join operation is done on HDFS.
C.  Map-side join is faster because join operation is done in memory.
D.  Reduce-side join because it is executed on a the namenode which will have faster CPU and more memory.

Answer: C