What's the best marijuana stock on the market right now? My pick would be Constellation Brands (NYSE: STZ). I think Constellation is the best marijuana stock. because of its great growth prospects and relatively lower risk compared to most marijuana stocks.

But Constellation Brands isn't a pure-play marijuana stock. Buying Constellation involves an investment in the company's alcoholic-beverage business even more than in the cannabis industry.

So what is the best pure-play marijuana stock on the market right now? If I could only buy one pure-play marijuana stock, it would be Constellation's partner, Canopy Growth (NYSE: CGC).

Why not a less expensive stock?

Yes, Canopy Growth's market cap of more than $15 billion is way more than every other pure-play marijuana stock around. Why wouldn't I choose a more attractively valued stock -- perhaps Aphria (NYSE: APHA) or OrganiGram(NASDAQOTH: OGRMF)? First, let me say up front that it wouldn't surprise me if Aphria and/or OrganiGram outperforms Canopy Growth this year.

Aphria's share price has been beaten down primarily by the allegations from short-sellers that the company drastically overpaid for its LATAM Holdings acquisition. OrganiGram is a great underdog Canadian marijuana producer that doesn't receive the attention it probably deserves in the U.S. investor community. I think it's likely that both of these situations change in 2019, with a review by a special committee of Aphria's board potentially clearing the air over the short-sellers' allegations and OrganiGram potentially listing on a major U.S. stock exchange.

However, I take a long-term view when it comes to investing. If I could buy only one stock in any industry, it would be the stock of the company that I think has the best chance of being a dominant player in the industry. And for the cannabis industry, in my opinion that stock isn't Aphria or OrganiGram -- it's Canopy Growth.

While Canopy looks a lot more expensive than most other Canadian marijuana stocks right now, my take is that it's best to look at what the future for the cannabis industry could hold. I expect that the global marijuana market could easily exceed $100 billion within the next 10 years and even more in subsequent years. If Canopy captures 10% of this market, the stock should be worth several times its current value.

The compelling case for Canopy

The global cannabis market is changing and expanding rapidly. I think that to be the biggest winner in this market, a company must be able to have the necessary production capacity to keep up with demand, have a strong distribution network in key countries, and have what it takes to stay ahead of the curve as the market grows. I think there's a compelling case that Canopy Growth checks off these boxes better than any other company.

Thanks to its flurry of acquisitions, Aurora Cannabis currently claims the biggest production capacity in the industry. But Canopy ranks as a strong runner-up and continues to bolster its production capacity through expansion and supply agreements with other cannabis producers.

When it comes to distribution networks, Canopy Growth arguably stands atop the field. The company has the broadest and strongest supply agreements deals among its peers for the recreational-marijuana market in Canada. It has a major presence in European markets, notably including Germany. Canopy is well positioned in Latin America, Australia, and southern Africa.

But perhaps the best reason to like Canopy Growth is its ability to stay ahead of the curve. Part of that ability comes from a strong management team. However, Canopy's relationship with Constellation Brands is a major factor as well. Canopy's deal with Constellation gave it a ton of cash to use in expanding internationally. It also provides Canopy a partner with expertise in building successful consumer brands.

A great example, in my view, of Canopy's ability to lead rather than follow is the company's plan to build a large-scale hemp production facility in New York. The recent U.S. legalization of hemp paves the way for a huge new market. While rivals are still saying they'd like to jump into the U.S., Canopy has already secured licensing in New York, forged positive relationships with key political figures, and will set up shop in the near future rather than stand on the sidelines waiting.

My biggest concern

Despite my bullishness about Canopy Growth's prospects, I know Murphy's Law has a way of rearing its head. My biggest concern is that it will take longer for cannabis markets around the world to grow than anyone expects.

There are plenty of ways that could happen. Countries might be slow in establishing regulations even after legalizing marijuana. Even if regulations are put in place quickly, they could be burdensome and hinder growth. And while the possibility that the U.S. marijuana market could open up for Canopy appears better than ever, there's no guarantee that federal laws will be changed anytime soon.

For all these reasons, Canopy Growth remains a high-risk stock for which many investors will want to steer clear. But for more aggressive investors with a long-term perspective, I can't think of a better, stronger pure-play marijuana stock to buy right now than Canopy Growth.