The complete cost of every path — not just the payment.
Your net position if you exited at any point in time: everything paid in — down payment, closing costs, every payment with taxes and insurance inflating — minus the equity you would actually walk away with after selling costs. The renting line is honest too: the renter invests the cash they didn't put down and gets credit for the growth. Lower is better.
Answers use the exact figures above — your scenarios, not national averages.