What is the difference between 3 times Edo Tensei have been used?


We have seen this jutsu performed three times during OG Naruto and Shippuden.

  * Orochimaru used Tobirama and Hashirama vs Hiruzen
  * Kabuto uses an army of Edo Tensei
  * Orochimaru Edo Tensei 4 hokages

Why the first edo tensei done by Orochimaru was considered weak? Also, he used
White Zetsu for 4 hokages while it is said it needs a living sacrifice.

