Question for everyone- Spokane

[David Walker]

I recently moved to Spokane Wa after leaving my house hacking duplex in Tri-cities. I am considering selling the duplex next month, after taxes and commissions- I will be at $40k profit. I am weighing the pros and cons between reinvesting in the Spokane market (i.e. 20% down on a 100k house and renting). Or... making $40k one-time principle payment on our primary home morgagte(252,000 owed).  Amortization schedules are saying that I would shave roughly 9 years off my loan, with an interest savings of $77k.  

What are your guys thoughts?  I appreciate you taking the time to give me feedback!!  :)