Marijuana stocks aren't all alike. MedMen Enterprises Inc. (NASDAQOTH: MMNFF) and CannTrust Holdings Inc. (NASDAQOTH: CNTTF) prove the point. Their business models are very different. MedMen is a U.S.-based company, while CannTrust is headquartered in Canada.So far this year, CannTrust has turned in a better stock performance than MedMen has. But which of these two marijuana stocks is the better pick for investors now?