The big muff has a bit of a reputation for being unpredictable as EH have always randomly changed circuits and transistor specs without notice, even within the same production run.
Try the pedals yourself, the russian model sounds different from the 'US' version (and theres variation within the russian ones too). So TBH I would not be 100% sure that the small verson sounds the same.
Try them, I have seldom found one that I didn't like but they do differ.
I prefer my own home built ones, with lower gain transistors (and tweaked diodes). I like to call it the sweet muff ;)
Don't bother with the Behringer clone it's really bad :(