Hello @Ram D,
There are several advantages with Kerberos over LDAP. The most prominent one is - Kerberos is more secured when compared to LDAP. Here's how:
1. Kerberos is conceptualized and implemented as authentication protocol from the beginning where the protecting the user's credential is given utmost importance. Whereas LDAP is actually a directory access protocol (a la telephone directory) and not meant for authentication originally.
2. User's password *never* travels over wire when using Kerberos. Of course, you can secure LDAP communication with SSL but then it is 'encrypted password' which is traveling over wire.
There are couple of reasons why Kerberos has been chosen by Hadoop world as de fecto authentication standard.
Hope this helps.