I guess you could use whichever would work best for your workflow. Deleting is more clicks. Also, as you stated, there is the record of past work. It may be useful to go back to a completed task for reference, especially if it has a lot of subtasks and notes included.

One way I handle abandoned tasks is to tag the task with a "discarded" tag, add a note explaining why the task was discarded, and then complete the task. I then have a Smart List with tasks that are tagged with that tag and are completed. So all of my abandoned tasks are in one place.

These things may not be helpful to you. I think there'd be nothing wrong with just deleting tasks as you complete them. Whichever works best for you.

Thank you, for the detailed response. Appreciate it.