I'm just speaking from experience. What I've actually seen. The original K/H pistons were made from bakelight. Stainless replacements ain't cheap. If you buy reman calipers with stainless replacement pistons they are even more not cheap. For my money, I like the single piston calipers. If you already have the K/H stuff, use it. But if you're contenplating a change to the larger bolt pattern, I would go with something different.
And yes, Chrysler changed to cut costs. But the design is cheaper to make, cheaper to provide parts for, cheaper to service, which makes the single piston caliper a better design.