London: Is the Overground an S-Bahn?

A Frequently Made Comparison, but a Good One?

I was recently reading something where a comparison between the transport networks of London and Berlin was being made, and the conclusion was that the S-Bahn in Berlin and the London Overground are basically the same type of system, and more or less of equal quality. I sort of thought that this was self-evidently not the case, but perhaps the distincti…