I got it being myself a huge SP fan, it's impressive how close you can get a SD tone with this pedal and some minor tweaks on the amp.
I had the PI NYC Big Muff (transistor versione) in the past, this is a better one if you're after the SP's vibe and tones.
I've never had the 70's old real Op Amp version so I cannot compare the 2, but from the rewiews i read and seen (from YT), it's really close to it.
The only little notice may be the spacing of the knobs, sometimes when adjusting the tone knob, it's easy to touch the knobs above, apart that the mini size is ok!