Tilray (TLRY) stock is on fire lately. I have nearly worn out my fingers typing about Tilray's share price continuing to set new all-time highs. But my fingers haven't moved much at all writing about Aurora Cannabis (ACB -2.84%) stock's recent performance.

It's not that Aurora hasn't enjoyed some really nice gains over the last few weeks. The marijuana stock is up around 37% in just the last month. Tilray's share price, though, has skyrocketed close to 350% during the same period. Until late August, Aurora was the No. 2 marijuana stock by market cap, trailing only Canopy Growth (CGC 0.20%). Now Tilray has not only topped Aurora. It has also leaped past Canopy to become the top marijuana stock in terms of market cap.

Why is Aurora Cannabis stock figuratively eating Tilray's dust? I think there are three primary reasons.

Pile of marijuana leaves with one leaf positioned at center of the top of the pile.

Image source: Getty Images.

1. Its stock isn't listed on a U.S. stock exchange

My view is that probably the single biggest reason why Aurora Cannabis hasn't performed nearly as well as Tilray is that its stock isn't listed on a U.S. stock exchange. Tilray conducted its initial public offering (IPO) on the Nasdaq in July.

The reality is that the U.S. is where many of the investors with the deepest pockets are. Tilray, Canopy Growth, and Cronos Group currently are the only Canadian marijuana stocks listed on U.S. stock exchanges. I don't think it's a coincidence that these three stocks have outperformed most others. Yes, Aphria (NASDAQOTH: APHQF) has risen more than Canopy and Cronos over the last month, but we'll get to why that's likely the case shortly.

Aurora is making an effort to drum up interest among U.S. investors. The company has participated in at least two online investor conferences of which I'm aware in attempts to raise its profile in the states. That just doesn't have the same impact as listing on a U.S. stock exchange, though. Aurora's vice president of investor relations, Marc Lakmaaker, said on Wednesday (during one of those online investor conferences) that the company will pursue a U.S. listing, but he didn't say when that might happen. 

2. It already had a sky-high valuation

Another reason why I suspect Aurora Cannabis hasn't generated the gains that Tilray has is that the stock already had a really high valuation before the latest surge started. In fact, Aurora's market cap was nearly double that of Tilray just one month ago.

There is one objection that might be raised about this point, though. Canopy Growth had an even higher market cap than Aurora did, and its stock has performed much better than Aurora's has. That objection is easy to address: Canopy received a $4 billion investment from Constellation Brands; Aurora didn't. Enough said.

That leads me to Aphria. I think that Aphria has performed better than most of its peers (Tilray excepted) because its stock was simply more attractively valued before the recent momentum for marijuana stocks kicked into high gear. My hunch is that had Aurora's valuation not been driven up so much earlier, its gains would have been comparable to other leading Canadian marijuana stocks. 

3. Concerns it could be passed up by major partners

My third reason for Aurora Cannabis trailing so far behind Tilray in stock performance is a little more speculative. I think it's quite possible that many investors are concerned that Aurora won't land a big deal with a major partner like Canopy did.

Constellation picked Canopy over Aurora. And although Aurora was reportedly in the top tier of cannabis partner candidates for Molson Coors Brewing, the big beer-maker instead went with HEXO, formerly known as Hydropothecary. Is it fair to bring up these instances since Tilray and others were passed over as well? Maybe not. But Aurora was the No. 2 largest Canadian marijuana grower when both of those decisions were made and it lost out to a rival each time.

Diageo could now be looking for its own cannabis partner. Aurora is probably on the short list for the big alcoholic beverage company. However, I think that Aphria and Tilray could have better chances of being picked than Aurora does.

Maybe it's for the best

Should investors be worried about Aurora's relative underperformance? I don't think so. Like I said earlier, the stock still generated fantastic gains over the last month or so. Aurora is the third-largest marijuana grower. I think that it's likely to snag a big partner, either from the alcoholic beverage industry or the tobacco industry.

Actually, I think more concerns would be in order if Aurora had skyrocketed as much as Tilray has. Most marijuana stocks are overvalued, in my view, at least looking at their growth prospects over the next few years. In my perspective, Tilray shareholders could have more to worry about right now than Aurora shareholders do.