Test plan and test case issue as a main or sub issue

[Certus Port Automation]

Hi People,

Im going to implement 2 new issue types and i am wondering if people know what would be the best. To implement those two as a sub issue under a development task and user story or to implement this a independent issue type.

is there anybody that can give some recommendations about this and what are the pros and cons regarding these ways of implementation?

Thanks already for answering.

Michel