Marijuana might technically be a commodity, but not all marijuana stocks are equal. Some have better growth prospects than others. Some are less risky than others. And some have performed much better than others.

On that last point, Aurora Cannabis (NASDAQOTH:ACBFF) definitely holds an advantage over Aphria (NASDAQOTH:APHQF). Both Canadian marijuana growers appear to have tremendous opportunities ahead of them, but Aurora's gains in 2017 easily topped Aphria's. So far this year, Aurora stock is up significantly, while Aphria stock is down.

But past and even recent stock performance doesn't provide insight into what might happen in the future. Which of these two marijuana stocks is the better choice for investors now? Here's how Aphria and Aurora Cannabis compare.

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The case for Aphria

Why would an investor consider buying Aphria stock? There really are just two primary reasons: rising medical marijuana demand and the potential opportunities for selling recreational marijuana. 

Aphria is already benefiting from higher demand for medical marijuana. The company is a licensed supplier of medical cannabis in its home country of Canada, and was the first among its peers to report positive operating cash flow and positive earnings in consecutive quarters. 

Business is booming in Aphria's core medical marijuana market. In the quarter ending Nov. 30, 2017, Aphria posted year-over-year sales growth of nearly 63%. Despite the rapid growth, though, the company's revenue totaled only 8.5 million Canadian dollars. That's low, especially considering Aphria's market cap of close to $2 billion.

But Aphria's revenue so far doesn't include significant contributions from the expanding international medical marijuana market. That could change soon. In January, Aphria announced its acquisition of Nuuvera. Aphria already had agreements to supply medical cannabis in Australia, but the combination with Nuuvera gives the company a presence in nine other international markets, including the large German market.

One market where Aphria has pulled back from, though, is the U.S. Aphria was moving full steam ahead with a U.S. expansion last year, but its plans were derailed when the Toronto Stock Exchange threatened to delist stocks of marijuana growers with significant U.S. operations. As a result, Aphria scaled back its U.S. exposure.

Aphria stands to enjoy a big boost when Canada legalizes recreational marijuana later this year. The company is expanding its production capacity to meet the anticipated high demand. By early 2019, Aphria should be able to produce close to 230,000 kilograms of marijuana annually with its own facilities and supply agreements with other growers. 

The case for Aurora Cannabis

The reasons for buying Aphria also apply to Aurora Cannabis. However, Aurora is positioned differently from Aphria.

For one thing, Aurora's medical marijuana business is larger than Aphria's. In its latest quarterly results, Aurora reported revenue of CA$11.7 million, more than tripling the total from the prior-year period. 

Aurora Cannabis is also already well positioned in international medical marijuana markets. Over one-fifth of its sales in the last quarter were made in Germany by the company's Pedanios subsidiary. In addition, Aurora has a presence in Australia, Denmark, and Italy.

The biggest story for Aurora in recent months has been its attempt to acquire CanniMed Therapeutics. Although CanniMed initially fought the takeover, the two sides eventually reached an agreement. The acquisition of CanniMed was a key driver that pushed Aurora's market cap to more than $4 billion.

Buying CanniMed was just one part of Aurora's strategy to position itself for the looming recreational marijuana opportunity in Canada. The company is also expanding its internal production capacity significantly. Aurora expects that it will be able to produce 240,000 kilograms of cannabis annually plus another 19,000 kilograms with the CanniMed acquisition.

But there's more to preparing for the anticipated new market than just boosting capacity. Aurora has also taken steps to be ready for retail sales of recreational marijuana. One key move made by Aurora was to buy a stake in Liquor Stores N.A. Ltd., which is converting some of its locations to cannabis retail stores and will build new cannabis retail stores. 

Better buy

In my view, both Aphria and Aurora Cannabis should enjoy tremendous sales growth over the next few years. The Canadian medical marijuana market could increase to around CA$3 billion annually, while the country's recreational market could be two or even three times that size. And the international medical marijuana opportunities are just getting cranked up.

But which marijuana stock is the better buy? I think the nod goes to Aurora. My decision boils down to readiness to take advantage of the coming opportunities. Aurora has greater internal production capacity than Aphria does. It has a head start in the lucrative German medical marijuana market and is positioned well to supply other European countries. In addition, Aurora appears to be in better position for retail sales of recreational marijuana in Canada.

Keep in mind, however, that Aurora's lofty stock price already assumes massive growth. While it is a better choice than Aphria, in my opinion, there certainly are risks to buying any stock with such a steep valuation.

Keith Speights has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.