Both Price and Sale do way better with Leon. If the differences are truly a result of who is catching them, that differential way out weighs the probable loss on offense between Vaz/Swi and Leon.
On salary: Vaz is slated to make- 19:$2.85M, 20:$4.2M, 21:$6.25M, 22:$7M club option ($0.25M buyout).
Leon makes $2.475M with one arb year left. If the arb guy agrees that he sucks, the Vaz-Leon salary difference will be much more next year. Vaz will likely make more than Leon & Swihart combined in 2020.