I am going to disagree @u0d4n7a0p as far as having a choice on paying down either the $150K acquisition debt or the $350K equity debt first. The refi on the primary home is a mixed-use mortgage consisting of both acquisition and equity debt. You have to apply all principal to the equity balance until it is paid down before applying principal to the acquisition balance. It doesn't matter if the equity portion was used to purchase a rental home.
The schedule A deduction is (acquisition debt balance) / (total mortgage balance) = 150K / 500K = 30% of the total mortgage interest paid. The remaining interest is a rental expense that can be reported on schedule E.
