I had an original early 80s Big Muff, which I always enjoyed playing with. As anyone who owned the original can tell you, the original is housed in a hug casing with most of the inside empty apart from the battery compartment and a small board. Now this has been shrunk down to this pint-size version.
Frequency pickers might find slight differences between this unit and the original units, but in a band situation or in a mix recording you really cannot hear the difference. It takes up much less space on the pedal board, standard 9v power socket and a good healthy click to switch off and on.
I still have the same fun as I had with the original Big Muff, but in a much more user-friendly size.
Still in my view, Big Muff is the best fuzz you can buy and this gives you THE fuzz sound which you can pay a lot more for in other brands and still don't get the sound.