Marijuana presents a massive growth opportunity for investors, especially as the U.S. moves toward legalizing the substance at the federal level. With Republicans recently introducing a federal legalization bill, the prospects grow for a bipartisan solution.

But many of the big, early cannabis players soared out of the gate quickly on the potential of exploiting Canada's newly legalized market, only to get burned and fall back down as that nation's regulatory morass proved more challenging than originally expected.

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Tilray (TLRY 1.60%) was one of those first run-and-gun stocks that's fallen hard in the aftermath, but it still holds enormous promise, particularly as hope remains high that the U.S. system won't fumble the ball in the same way Canada did.

Here are two particularly strong arguments for the bull and the bear case for Tilray:

Bear case: There are too many better pot stocks.

Keith Speights: Sure, Tilray's acquisition of Aphria has made it a force to be reckoned with in the cannabis world. And yes, the company's track record of 10 consecutive quarters of growth in adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) is impressive. My biggest problem with Tilray, though, is that there are simply too many other pot stocks that are better picks.

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Tilray's goal is to achieve $4 billion in annual revenue by 2024. But as our Motley Fool colleague David Jagielski recently pointed out, the company will almost certainly need to make another acquisition to hit that target. This would inevitably mean more dilution is on the way.

Meanwhile, there are several U.S. cannabis operators that have a much easier path to growth. Some of them consistently generate adjusted EBITDA that blows Tilray out of the water. As icing on the cake, their valuations are more attractive than Tilray's.

As a case in point, Cresco Labs has great growth opportunities in multiple states. The multi-state operator (MSO) reported adjusted EBITDA of $56.4 million in the third quarter. Yet Tilray's price-to-sales multiple is more than two times higher than Cresco's. 

Cresco isn't alone. There are other U.S. MSOs with similar stories. Why settle for Tilray when there are better alternatives?

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Bull case: There's no pot stock with better potential.

Rich Duprey: As the largest marijuana stock by market cap, Tilray's pre-eminent position in the industry presents it with both opportunity and challenges. 

The largest lever for growth comes from its acquisition of Aphria, which gives it a global recreational, medical, and pharmaceutical distribution business, as well as its more recent investment in MedMen (MMNF.Q), the U.S. marijuana retailer. They provide the pot stock with the chance to break out from the recalcitrant Canadian market. 

Although each market is currently walled off largely by specific geographies -- recreational marijuana is primarily in Canada, medical marijuana is largely in Europe and Australia, and the pharma operations are in Germany -- the intent is to eventually have them merge everywhere.

The MedMen deal gives Tilray rights to about a 21% ownership stake, and access to 25 stores in six states including California and Florida. The $80 billion U.S. market is the world's biggest, and federal legalization could be a transformative event for Tilray's entry.

It also has U.S.-based hemp and cannabidiol (CBD) businesses, as well as the craft brewing operations of SweetWater Brewing, which it acquired last November

While the effect hasn't paid off for Tilray just yet, with fiscal first-quarter results missing expectations last month, the business is still growing. And most of the levers to be pulled represent future potential, not immediate results. The scale of its operations and breadth of its products and services give Tilray unparalleled excellence globally, and its beaten-down stock will seem priced for the bargain basement when looking back in time.