Suppose you bought $10,000 of Aurora Cannabis (ACB -7.01%) stock five years ago and held onto those shares. How much would your initial investment be worth today? Around $91. Ouch.

With that abysmal performance, you might think making a case for investing in Aurora Cannabis today would be an exercise in futility. But that's not necessarily so. Here's the single best argument for buying Aurora Cannabis stock right now.

Four important words

I think the best argument for investing in Aurora Cannabis can be summed up in four words: Brighter days are ahead. If these four words are true, buying the heavily beaten-down marijuana stock could pay off nicely. But are they true?

There are definitely some reasons to believe that the worst is over for Aurora. For example, the company achieved positive adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) in its latest quarter. While that's not the same thing as true profitability, it's nonetheless a huge milestone for Aurora that's taken a long time to happen. 

This positive adjusted EBITDA shouldn't be a fluke, either. Aurora Cannabis CEO Miguel Martin stated in the company's fiscal 2023 second-quarter conference call, "We are confident that we can deliver positive adjusted EBITDA on an annualized basis going forward." Martin acknowledged, though, that there could be some quarters when adjusted EBITDA dips into negative territory due to the volatility of the cannabis industry. 

Delivering positive adjusted EBITDA is certainly a step in the right direction for Aurora. However, that by itself isn't a compelling reason to consider buying the stock.

Big potential catalysts in Europe

On the other hand, Aurora's big potential catalysts that could be on the way in Europe could make the stock much more attractive. In particular, developments in Germany could lead to huge opportunities for the company.

Martin said in the recent quarterly call that Germany should provide "further clarity around recreational legalization" this spring. Adult-use cannabis could be legalized in the country as early as 2025. To put this market opportunity into perspective, Germany's population is more than twice the size of Canada's population.

Aurora Cannabis should be in a prime position to be a top player in Germany's recreational cannabis market. It's currently one of only three medical cannabis producers with domestic production licenses in the country. This status seems likely to give Aurora a competitive advantage as Germany moves forward with its recreational cannabis plans.

Even better for Aurora, Germany could be just the tip of the iceberg for European recreational marijuana legalization. Other European Union countries, including the Czech Republic and Poland, could follow in Germany's footsteps.

There's also an opportunity for Aurora to receive a boost in Germany's medical cannabis market. The country has a major effort underway to reduce red tape with its medical-qualification process for medical cannabis. Currently, only around 30% of patients who seek medical cannabis make it all the way through the process. Aurora thinks that some enhancements could be announced relatively soon that could clear the way for more patients to be approved for using medical cannabis products. 

Is the best good enough?

My view is that brighter days really could be ahead for Aurora Cannabis with its improved financial position and potential catalysts in Germany and other European countries. I believe this is the best argument for buying the stock right now. But is the best argument a good enough reason to invest? That's a different story.

Aurora continues to lose money. It's not clear at this point how soon the company will turn a profit. Significant headwinds are likely to prevail in the Canadian cannabis market for some time to come. Canada remains the most important market for Aurora.

The strongest argument against buying Aurora Cannabis is that there are too many other stocks that offer more attractive risk-reward profiles. I think that the best case against investing in Aurora outweighs the best case for buying the stock, at least for now.