I've used both and I seem to get greater results with Russian's, but they also seem to produce greater sides (bloat, indigestion, etc...). I don't know if there's any truth to the old rumor that Russians sometimes come adulterated with extra ingredients like methyl-testosterone in the mix. Or if it's simply the binder's used in the Russian's that give some people (including myself) stomach problems.
But neither one is gonna kill you... So why not just try a cycle of each and make up your own mind about which one works better with your body chemistry...?