The quality does not depend as much of the country of origin as it does with how the vendors have been handling and storing it. For highest quality you want to get almost freshly dried MHRB, not something that has been in store for several years. (Small vendors may have very little MHRB in store at a certain time, thus they have 'fresher' powder, as opposed to the big ones) Also one should note that if you order directly from mexico/brasil, it is more likely to be recently harvested, than if you order from some other country (whom act like a middleman storing it).
Ah yeah, i have to agree with Contact, that vendor has some fresh MHRB (I've heard, hasn't got any experience yet)! Just a shame they can't harvest at the moment.
There's a clear difference between what I say I do and what I actually do perform.