As the legal medical marijuana industry in Canada has taken off, a small group of stocks of marijuana growers has vaulted to multibillion-dollar market caps. Other Canadian marijuana stocks, however, haven't become that highly valued. Canopy Growth Corporation (NASDAQOTH: TWMJF) is an example of the former group, while Organigram Holdings (NASDAQOTH: OGRMF) belongs to the latter category.But current market cap and past performance aren't good predictors of future success.