I think a lot of people forget that it all boils down to the money.. If you have the finances or scholarships that will cover the cost of a different degree AND flight training that's probably the best option. Sadly for most of us that's not the case. For myself I needed the aviation degree because no one would lend me money to finance flight training, but the second my state university called my rating a "lab class" I could get all the financial aid I needed. I've had a lot of acquaintances try and do the pay as you go route for flight training. The problem with that is they are just now 6+ years later hitting regional pilot mins or gave up the career all together, while I'm starting at a major airline. Sadly money tends to make the decision for most.

TL/DR: In a vacuum a unrelated 4 year degree is best, but in the real world money makes the decision.