Below are main difference between JIRA and Bugzilla
(1)JIRA:-Jira is one of the famous commercial tool these days.
(1)Bugzilla:-On the other hand Bugzilla is an open source tool.
(2)JIRA:-When we say about the user friendly feature it is more suitable then Bugzilla.
(2)Bugzilla:-It is less user friendly when we compare this with JIRA.
(3)JIRA:-We can do prioritization of issues by doing drag and drop in JIRA.
(3)Bugzilla:-Here we donot have such feature of drag and drop.
(4)JIRA:-One of the best feature of JIRA is that it has configurable link types with userdefine semantics and we can also create pluggable remote issue links which means this allow to link an issue to any other entity outside JIRA.
(4)Bugzilla:-On the other hand Bugzilla has only one link type blocks/depends and a BugID custome field.
(5)JIRA:-In JIRA we can define multiple workflows and these are applied on the base of issue project and type.
(5)Bugzilla:-Here this tool provide the user a facility to select the initial status of a new issue.
(6)JIRA:-There are numbers of custome fields types avilable in JIRA. And also have more custom fields types available from plugins.
(6)Bugzilla:-There are limited number of custom field types available in Bugzilla and these are Text Fields, Multiselection, DropDown, data/Time and BugId.
(7)JIRA:-Here we can also apply conditional configuration on base of Project and Type fields.
(7)Bugzilla:-Bugzilla helps us to show/hide the whole custom field or specific values based on the value of some other field
(8)JIRA:-JIRA has lacks of advance-level search options. But JIRA have flexible JIRA query Language that helps us to build arbitrary boolean expressions.
(8)Bugzilla:-On the other hand Buzilla comes with a powerful advanced search option.