 Solution

Class inheritance offers a compact specialized implementation: the scaled sum is also a SumChannel and can be used where that concrete type is required, while its inherited state handling is reused directly.

The decorator supports run-time object composition over any Channel implementation, including an already constructed stateful software object, without editing or subclassing each concrete software class. Its extra software object and delegation are a small cost. The two approaches therefore serve different reuse needs; the wrapper need not pretend to be the concrete sum-channel software class.