Hate to say it, but you need to search...
The Russian pedals have been discussed in detail before - especially the Russian Big Muff (and its Sovtek predecessor).
Generally, they work just as well on bass as their American counterparts, and they aim to create the same effect... but they do sound different. Not hugely different, IMO, but enough that you might want to try them side-by-side. Also, there are more variations in build quality and sound between the Russian pedals than you'd ever see in most modern EHX pedals.
Fuzz enthusiasts spend their time arguing about the Russian versus American Big Muffs. The Russian is generally regarded to be harsher and bassier, while the American (NYC) is generally thought to be warmer but has less low end retention. The Little Big Muff (also an American-made Muff) is more like the American, but with tons of low end.
