It is an Open Source
It is a commercial tool
Using Bugzilla might be little complicated for few due to grouping users and granting permissions
For some using JIRA would be more convenient than Bugzilla
Bugzilla allows you to show/hide the whole custom field or specific values based on the value of some other field
JIRA enables conditional configuration based only on Type fields and Project.
Bugzilla’s has a powerful advanced search option
JIRA lacks advance-level search options. JIRA has a flexible JQL language (JIRA Query Language). It enables you to build arbitrary boolean expressions.
Unlike JIRA, Bugzilla allows users to select the initial status of a new issue.
Unlike Bugzilla, JIRA enables you to define multiple workflows which are applied based on the issue’s Project and Type.
Bugzilla has only one link type: Blocks/depends and a Bug ID custom field
JIRA has configurable link types with user-defined semantics. JIRA enables to link an issue to any other entity outside JIRA.