Here's a quick trivia question for you: What are the three largest U.S.-based marijuana stocks by market cap? If your answers included MariMed (NASDAQOTH:MRMD) and MedMen(NASDAQOTH:MMNFF), pat yourself on the back. (The third correct answer -- and the biggest of them all -- is Scotts Miracle-Gro.)

Determining the market caps for the biggest U.S. marijuana stocks is easy. Figuring out which of them is the better stock to buy is another story altogether. Which stock is the more likely to emerge as the biggest winner over the long run: MariMed or MedMen? Here's what you need to know.

The case for MariMed

MariMed's business model has worked so well that the company is changing it. How?

The company achieved its initial success by providing professional management services to the cannabis industry. These services included developing production facilities that are leased to customers, helping customers obtain state licenses for cannabis production, and other types of consulting.

Along the way, though, MariMed saw that its expertise was too valuable to use only in consulting. So the company began gobbling up its customers. MariMed is in the process of consolidating the ownership of the operations of its customers in the cannabis industry.

When all is said and done, MariMed should have operations in six states: Delaware, Illinois, Maryland, Massachusetts, Nevada, and Rhode Island. All of these states allow the legal use of medical marijuana, and two of them -- Massachusetts and Nevada -- also legalized recreational marijuana. Illinois might not be too far behind in legalizing recreational marijuana as a result of the November elections.

But MariMed isn't limited to just these states. The company plans to expand into other states with medical and/or recreational marijuana markets. 

Perhaps the most potentially transformative deal for MariMed, though, is its recent investment in and partnership with GenCanna, which specializes in the production of hemp. If the 2018 Farm Bill becomes law, the U.S. market will open up for hemp-based CBD products. Brightfield Group projects that the global hemp-based CBD market will reach $22 billion by 2022.

MariMed hasn't thrown in the towel on providing professional services for the cannabis industry, though. The company recently acquired BSC Group, which provides operational, marketing, and licensing management services to cannabis businesses.

The case for MedMen

MedMen is sometimes referred to as "the Apple Store of weed." And for good reason. MedMen's upscale California retail cannabis stores actually beat Apple on a key sales metric: revenue per square foot.

The company currently operates cannabis dispensaries in California, Nevada, and New York. But MedMen has also acquired additional properties and businesses in other states, notably including Arizona and Florida. These states should provide significant opportunities for growth.

However, MedMen isn't stopping there. The company announced in October that it plans to buy PharmaCann in a $682 million transaction that will go down as the biggest deal in the history of the U.S. cannabis industry so far. 

Assuming there aren't any snags in the PharmaCann acquisition, MedMen will become the largest marijuana business in the U.S. Its footprint will expand to 12 states, adding Illinois, Maryland, Massachusetts, Michigan, Ohio, Pennsylvania, and Virginia. MedMen's licenses after the deal finalizes will allow it to operate up to 66 retail locations and 13 cultivation/production facilities.

How big will the company's potential market be after it absorbs PharmaCann? MedMen will be a leading cannabis retailer in areas with a projected addressable market of $40 billion by 2030. 

While MedMen's primary focus is on the huge U.S. market, it's also hoping to win in Canada. MedMen and Cronos Group teamed up to launch retail cannabis stores throughout Canada where they're allowed.

Better marijuana stock

Both of these stocks appear to have strong growth potential. I think that MedMen gets the nod, though. Why? My view is that MedMen's focus on retailing will allow it to differentiate itself more than MariMed will be able to do as primarily a producer of a commodity.

However, I wouldn't call either of these stocks a must-buy just yet. I'd like to see MedMen's deal with PharmaCann finalized first. Still, my take is that investors should keep both MedMen and MariMed on their radar screens.