Configuration variables are, in my experience, considerably more error prone. If something is in a configuration file, some day, somebody is going to want to c

Configuration variables are, in my experience, considerably more error prone. If something is in a configuration file, some day, somebody is going to want to configure it, not knowing how it works, what the valid values are, or what it even does. Moving something to a configuration variable means you have to do all the work to sanitize that input and defend against invalid values. Hearing "Oh, make setting XYZ configurable" or "Stick a flag to turn FooBar'ing on or off" also fills me with worry, as all too often it has been the harbinger of terrible feature creep and piling on of technical debt.