The Inserts both execute at about the same speed. It is the "Select where not in" statement that is considerably slower with the table variable. So I think...

I haven't proven this correct yet, but I am thinking redundant data in two tables makes sense if you need that data to join the tables properly and avoid table/index...

I would argue that sometimes you may have redundant data in your database to make reporting easier and faster.

Things have certainly improved in my career from last year. I spent the last several years at one company that basically did an about-face and stopped taking its IT...