I guess the point is if you are investing instead of paying off debt, you are in at least the same position theoretically, and hopefully much better because you have had good gains on your investments. Even with large losses in 08-09, my rate of return has been many multiples of 3%. Of course if you invest poorly, or the market completely crashes, that is another story.
So a paid off $30k car (depreciating asset) with $0 investments is no better, and likely worse than a financed car with $30k invested gaining a return.
If you lose your job, you risk losing your house regardless. If your car is paid off, you can sell your depreciating asset for a loss under scenario 1 to pay for your house, or withdraw from your appreciating investments under scenario 2.
How about other scenarios? You get sued for $1M when a tree in your yard falls on someone. Your business with personal guarantees fails? Etc... Some states have homestead exceptions to allow you to keep your home. Many do not. Your retirement account would be protected. Retirement accounts are protected from everything except IRS taxes and Qualified Domestic Relations Orders.
I'd put my house in a retirement plan if ERISA allowed me to.