If C.P.U and I/O devices are nearly same at speed, the buffering helps in making the C.P.U and the I/O devices work at full speed in such a way that C.P.U and the I/O devices never sit idle at any moment.
Normally the C.P.U is much faster than an input device. In this case the C.P.U always faces an empty input buffer and sits idle waiting for the input device which is to read a record into the buffer. For output, the C.P.U continues to work at full speed till the output buffer is full and then it starts waiting.
Thus buffering proves useful for those jobs that have a balance between computational work and I/O operations. In other cases, buffering scheme may not work well.