Contractors and customers frequently engage in the condensing vs. cast iron boiler debate. It’s incumbent upon contractors to paint the full picture for customers, rather than simply presenting the cast iron option and its lower purchase price. History LessonIn the past, a cast iron boiler was a safe bet for homeowners. Today, this big plus for cast iron boilers has been removed. Cast iron boilers now have technology similar to condensing units, but they are now more expensive to maintain.