if im not wrong swollen pickle is basically a big muff clone, with more controls.
the choice is simple, unless you have a very specific preference for the original big muff tone, which im guessing you dont, since you are considering both the nyc and sovtek muffs which supposedly sound different.
i've never tried it but i did a muff and i find that the muff is completely useless on high 'sustain' settings, on top of being very compressed.