Those old benchmarks (that have since been deleted) are highly misleading. The protobuf column is essentially what you would get if you just ignored all the performance best practices of protobuf. There's no reason why in C++ you'd need to allocate and deallocate a message struct for every parse. You just reuse it. And you can have allocation-free parses if you want, and you can alias network or file buffers if you want.

But the main reason people use protobuf is it is compact, which this table does accurately show. Flatbuffers are always larger.