This or That scenario? Stock to pay off Mortgage

[Ronin Crimmons]

Should we use stock assets to pay off home mortgage?

Details:

550K mortgage at 3.5% with 29+ years left to pay (purchase price 1 mil)

Currently have 550K in stock that we could use to pay off mortgage 

The stock is not part of our 401k plans.  We have a sufficient rainy day fund and the stock is not factored in to our our overall investment goals; however, it would obviously help us reach those goals sooner.

Interest savings would be 350K + over the life of the loan

Should we keep the money in the stock market or pay off our mortgage considering Trump capped the interest deduction at 10k and our property tax more than reaches that threshold??

Thank you for your insight