Is there ever a instance where it is actually a better deal to do a 30 year and make extra principal payments instead of just a 15 year?
Besides the flexibility of having the extra money
If you just plan to make the extra principal payments on the 30yr, then yes the only benefit over a 15yr would be flexibility. But that flexibility comes with the cost of a higher interest rate and more total interest paid over the 15 year period. However, instead of making the extra payments on a 30yr, another option is to make regular payments but invest the difference between what you would pay on a 15yr. This would be the most beneficial scenario given you can find investments with an expected return greater than the interest rate on the mortgage.
1 extra payment in year or bi-weekly payment can cut approximately 7 years of mortgage in 30 year fix. 15 year fix is good option but payment is higher and as an investor your DTI goes higher when you go for another deal.
Is this your personal home or a rental.
If a rental you do not want to pay down the mortgage. Doing so reduces "true" cash flow. You do not benefit from hoarding cash in a rental property.