Question received: is there ever a good reason to put more than 5% down on a new purchase mortgage?

yes, by putting a down payment of 20% or more than you can eliminate Monthly PMI that would be added to your payment which increases your monthly payment, and sometimes PMI can be difficult to remove once its added to the mortgage payment.  Also, by putting down 20% or more the seller will look more favorable at yoru offer to purchase than another  offer with a lesser down payment making it easier to have your offer accepted.

No, as long as you have excellent credit then your monthly PMI will be very low each month, and you will be better off financially by saving your down payment money and investing it.

The answer to this question totally depends on every borrower's situation.