What I mean is: do we actually need the kal va-chomer argument in the places where it’s used, or is a binyan av really enough? After all, kal va-chomer says that if law x applies to a, then in b, which is a lighter case with respect to the law under discussion, it obviously applies there too. With a binyan av, we see that you don’t need to find a more stringent side in order to say that a law applies elsewhere; it’s enough to say that if a has law x, and b is equivalent to it, then that same law will apply to b.

Obviously it works similarly. But when there is a kal va-chomer it is stronger, because there is a hierarchy. I wrote in the past that kal va-chomer is a kind of binyan av, unlike those who held that it is deduction, such as Adolf Schwartz. See the Talmudic passage in Chullin 115b–116a regarding the differences in even the slightest refutations.