Your rental income only covers the mortgage? Sell! If you want to own a rental, find one that actually makes money, not loses it. (There are plenty of threads here on how to figure that out.)
Too little info. Is the mortgage a 15yr or less term? What's the rate? If so, rent just covering mortgage may be OK. Is the local seller's market strong? How is the rental market?
Instead of cash flow, perhaps the OP is simply building equity more quickly. Then there's the deductions on overall income.
That said, remote land-lording may not be the OP's cup-o-tea. Also, the OP may be too heavily loaded on Real Estate if they don't have many other assets.
This probably comes down to doing the math and how comfortable (2) mortgages will or won't be.
One thing I STRONGLY discourage the OP from focusing on is DEBT alone. That's only one side of the balance sheet. Its really all about Net Worth...or more to the point...NW GROWTH. Choose the path that maximizes that.