I voted for Classes only because when a simple stateful object is needed the syntax is easier to read and its logic flow to reason about.
That being said, it is imperative for everyone here to understand that class is just syntactical sugar for prototypes AND because of this it is inherently limiting. So I wish there was a third option: depends/both. In simple use cases that 1) don't need complex inheritances (e.g., multiple parents) and 2) that are unlikely to radically change in the future and be depended upon by other objects I'd prefer the simplicity of class. In all other instances, use function prototypes or extended/concatenated objects with factories.