What is the difference between JIRA's LDAP integration and Crowd's JIRA integration?
JIRA's LDAP integration only delegates authentication to LDAP. This means that you still need to create groups and users in JIRA, and those users must have usernames that match your users in LDAP.
When you use Crowd's JIRA integration, all user and group management is delegated to Crowd. This means that you no longer have to create users and groups in JIRA. Crowd gives you access to all these users and groups in your underlying LDAP directories.