Selecting the wrong programming paradigm can lead to brittle code and unmanageable bugs. While functions excel at processing linear data flows, classes are indispensable for managing complex, mutating state. This guide provides the decision framework necessary to architect clean, testable software without falling into the trap of over-engineering.

Software development often suffers from the 'Java-fication' of code, where rigid hierarchies and unnecessary boilerplate stifle innovation. By embracing a hybrid approach that mixes functional logic with lean object-oriented structures, developers can build systems that are both powerful and maintainable. The secret lies in knowing when to use a class and when to simply let a function do the work.