Apples and oranges. That expression may come to mind when choosing between investing in Scotts Miracle-Gro (NYSE:SMG) and GW Pharmaceuticals (NASDAQ:GWPH). The former is a major supplier of lawn and garden products while the latter is a biotech focused primarily on rare diseases. But both Scotts Miracle-Gro and GW Pharmaceuticals also represent alternatives for investing in marijuana.

Which of these very different marijuana stocks is the better pick for long-term investors? Here's how Scotts Miracle-Gro and GW Pharmaceuticals compare.

Woman with palms facing up in front of chalkboardrawing of scales

Image source: Getty Images.

The case for Scotts Miracle-Gro

First, let's look at Scotts Miracle-Gro's credentials as a marijuana stock. Scotts' Hawthorne Gardening subsidiary is a top supplier of hydroponics products for the marijuana industry. And the cannabis market is becoming an even more important revenue source for the company.

In April, Scotts Miracle-Gro announced plans to acquire Sunlight Supply, the largest distributor of hydroponics products in the U.S., for $450 million. The deal is expected to double annual revenue for Hawthorne, with a large portion of that revenue stemming from sales to marijuana growers.

Scotts Miracle-Gro appears to be well-positioned to benefit from growth in the North American marijuana industry. Canada is set to legalize recreational use of marijuana this summer, and more U.S. states are considering legalizing either medical or recreational weed. There's even a possibility that U.S. federal laws prohibiting cannabis could be relaxed to allow states to make their own decisions without worries about federal interference.

But while Scotts Miracle-Gro is definitely looking to the marijuana market as a growth driver, over 90% of the company's total revenue still comes from sales of consumer lawn and garden products. Although fiscal Q2 sales for this business segment slid year over year, the culprit was mainly that an unusually cold spring season resulted in a late start to the typical lawn-and-garden season in much of the U.S. Over the long run, the consumer business should generate solid growth for the company.

Don't expect Scotts Miracle-Gro to deliver awe-inspiring growth over the next few years. However, the stock's total return should be quite good. Wall Street analysts project that the company will increase its earnings by 9.5% on average annually over the next five years. That growth, combined with Scotts' dividend (which currently yields 2.43%), should make the stock a market-beating investment.

The case for GW Pharmaceuticals

You might come away disappointed if you focus on GW Pharmaceuticals' current financial performance. The company's sole product on the market right now is Sativex, a cannabinoid mouth spray approved in 30 countries for treating multiple sclerosis-related spasticity. That list of countries doesn't include the U.S., though. Sativex hasn't been a huge commercial success so far.

However, things should be about to change in a big way for GW Pharmaceuticals. The biotech hopes to win Food and Drug Administration (FDA) approval in June for cannabidiol (CBD) product Epidiolex as a treatment for Dravet syndrome and Lennox-Gastaut syndrome (LGS), both of which are rare forms of epilepsy. The chances of obtaining that approval appear to be pretty good, especially since an FDA advisory committee voted unanimously to recommend that Epidiolex be approved in both indications.

Market research firm EvaluatePharma thinks that Epidiolex could be one of the 10 most successful new drugs launched this year. The firm projects that the drug could generate annual sales of close to $1 billion by 2022. Others are even more positive, estimating that Epidiolex could rack up sales of more than $2 billion.

FDA approval for Dravet syndrome and LGS should be just the beginning. GW Pharmaceuticals also is seeking approval for the two indications in Europe. In addition, the company is evaluating Epidiolex in a phase 3 study for the treatment of tuberous sclerosis, a rare genetic disease in which benign tumors grow on patients' brains and other organs. Epidiolex also is in a phase 2 clinical study targeting infantile spasms.

GW Pharmaceuticals' pipeline includes several other candidates, as well. The company is conducting a phase 3 study of Sativex in multiple sclerosis spasticity in hopes of winning U.S. approval. It also is testing a cannabidivarin (CBDV) product in treating epilepsy and autism spectrum disorders. Other cannabinoids are being evaluated for the treatment of neonatal hypoxic-ischemic encephalopathy (brain injury in infants caused by oxygen deprivation), glioblastoma (an aggressive form of brain cancer), and schizophrenia.

Better buy

I fully expect Epidiolex to win FDA approval. And while some are skeptical about the drug's commercial prospects, I suspect that Epidiolex will be a solid success story for GW Pharmaceuticals. I also think that GW stock has more room to run, even after its nice gains so far this year.

But is GW Pharmaceuticals a better marijuana stock than Scotts Miracle-Gro? Not in my view. Scotts Miracle-Gro has seen its stock price fall more than I think is warranted. That sets the stock up nicely for a big rebound when good news eventually arrives -- and I believe it will.

Scotts' disappointing financial results this year have been primarily caused by two issues: a late start to the lawn-and-garden season and speed bumps with California's processes for its new legalized recreational marijuana industry. Both of these issues only are temporary, though.

Over the long run, I think that Scotts Miracle-Gro stock will produce solid total returns for investors. It might not be as exciting as some marijuana stocks, but remember who won the race between the tortoise and the hare.

Keith Speights has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.