Have some cash - payoff rental or invest it?

[Paul Doherty]

I have enough cash to pay off one of my rentals, which would increase my cashflow by about $600 a month (house rents for $1375 and currently cashflows about $400).

Question is, would I be better off simply leaving that house not paid off, with its lower cashflow, and simply invest that same cash into a taxable investment account like Betterment or Wealthfront?  Do any tax advantages on the rental while money is still owed on it outweigh this as an option?