Scotts Miracle-Gro (NYSE:SMG) and Cara Therapeutics (NASDAQ:CARA) are both great growth stocks  that can provide investors with some terrific long-term returns. However, both companies are at very different points in their growth, and below I'll take a look at which one is a better buy today.

Investors have been much more bullish on Scotts over the past 12 months, with the stock's 39% returns eclipsing what Cara has done over the same time period:

CARA Chart

CARA data by YCharts

While Scotts has seen some softness lately, likely to do with cannabis stocks' struggle of late, its returns have remained very strong. Cara, however, shouldn't be so easily brushed aside, as its stock has enjoyed very strong performances in the past and over the last five years it has actually outperformed Scotts.

Getting involved with cannabis has given Scotts some life

What's made Scotts such an electrifying buy this year is that while the company has a strong core business around gardening, its marijuana strategy is what is getting investors excited about its potential.

Cannabis greenhouse

IMAGE SOURCE: GETTY IMAGES.

Through its subsidiary, Hawthorne Gardening Company, it has been able to help cannabis companies get up and running without actually having to take on the risk of growing or selling cannabis itself. It's great from a risk standpoint, and it has been generating strong sales growth for the company as well. Without cannabis, there wouldn't be nearly as much growth for Scotts, and as more cannabis operators come on board looking to cash in on the industry, Scotts will likely continue to benefit from that excitement. 

Many cannabis companies today are not only unprofitable but very volatile as well. For risk-averse investors, Scotts is a way to take advantage of the growing popularity of marijuana in a much safer way.

Succes of Korsuva has been key to Cara's growth

What's made Cara such an attractive investment over the years has been the success of its Korsuva drug, which targets the treatment of patients suffering from pruritus associated with chronic kidney disease. With strong results in its Phase 3 trials, the drug is showing a lot of promise. Meanwhile, trials for the company's Oral Korsuva are still in Phase 2. 

According to data collected by Cara, more than 30 million people in the U.S. suffer from chronic kidney disease, and one-third of the patients diagnosed in 2017 had prescriptions to stop itching related to it. It's a significant market opportunity, and Cara believes that patients have received inadequate relief. That's where the company can fill a significant need for patients in the near future. 

While the company is making good progress, and there's clearly lots of potential for it to continue to grow, it remains a long-term play for investors today. In its most recent quarterly earnings, the company's license and milestone fees totaled $5.2 million. While that was a big 81% improvement from a year ago when it generated just $2.9 million in sales, it's still nowhere near enough to cover the company's operating expenses, which reached $29.4 million, the bulk of that ($24.4 million) coming from research and development.

It could be years before Cara's Korsuva products become common treatment options for patients. But if that happens, the company's value could soar from its relatively modest $900 million market cap. Unfortunately, the stock is going to look pricey in the meantime since investors are ultimately paying for its potential. Normally a multiple of 45 times earnings would scare investors away, but given what it could achieve over the long term, it could prove to be a good price for the stock.

Why Scotts is the better buy today

Cara could very well produce better returns over the next five years, but there are also no guarantees that the stock won't run into issues during clinical trials, which could derail its potential. Scotts is much more of a certainty for investors today. While there are questions surrounding the cannabis industry, even if the status quo is maintained, there will be ample room for the company to continue to grow its sales as the legal marijuana markets in many states are still in their very early stages.

When in doubt, investors are better off siding with a more predictable investment. And with Scotts trading at a very reasonable 15 times earnings, the stock could offer great value for the growth that it may be able to deliver. Its 2.3% dividend only sweetens the deal even further.