If you're looking for stocks that have made tremendous comebacks in 2018, Opko Health (NASDAQ:OPK) and Myriad Genetics (NASDAQ:MYGN) definitely fit the bill. Opko stock was down nearly 20% this year before roaring back. Myriad Genetics saw its share price plunge close to 40% earlier in 2018, but a strong rebound has the stock price close to where it began the year. 

Which of these two comeback stories is the better choice for investors now? Here's how Opko Health and Myriad Genetics stack up.

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The case for Opko Health

Opko Health's Q1 results are a great place to start in determining why investors might want to consider the stock. After a painfully slow launch, secondary hyperparathyroidism (SHPT) drug Rayaldee began to enjoy some decent momentum. Total prescriptions for Rayaldee soared 730% year over year and jumped 38% higher than 2017 Q4.

Some analysts think that Rayaldee could reach peak annual sales in the ballpark of $700 million. There's a long way to go to hit that mark, but for the first time in quite a while, there's reason for some optimism about the drug.

The biggest source of revenue for Opko, though, is BioReference Labs (BRL). BRL is the third-largest clinical laboratory in the U.S. It focuses on genetic testing. In addition, BRL's sales team markets Opko's 4Kscore prostate cancer test. The business hasn't performed all that well in recent quarters. However, Opko put a new management team in place and thinks that BRL's revenue will improve in 2018.

Opko could have several new products on the way. The company hopes to get a green light soon from the FDA for marketing the Claros point-of-care prostate cancer test. A phase 3 clinical study is in progress evaluating human growth hormone product hGH-CTP in treating growth hormone-deficient children. The company also has several phase 2 pipeline candidates, including an experimental drug targeting treatment of benign prostatic hyperplasia, as well as type 2 diabetes and obesity drug OPK88003. 

One other reason many investors like Opko is the company's CEO, Phillip Frost. Frost is a billionaire with a long track record of success in the pharmaceutical industry. He has remained enthusiastic about Opko's prospects despite challenges through the years and has invested heavily in the company. 

The case for Myriad Genetics

Looking at Myriad Genetics' latest quarterly results also highlights the key arguments for the stock. Myriad topped expectations in fiscal Q3 thanks to surprisingly strong volume for its hereditary cancer testing. But the molecular diagnostics company has expanded into additional higher-growth areas, especially personalized medicine.

Myriad's most promising personalized medicine product is GeneSight, a genetic test that helps determine which antidepressant is best-suited for a particular patient. Myriad thinks that the global market size for this diagnostic test could be close to $10 billion. The company recently reported results from a large study that showed that patients with major depressive disorder (MDD) were 50% more likely to achieve remission and 30% more likely to respond to treatment when GeneSight was used to determine the appropriate medication.

The company also won FDA approval earlier this year for BRACAnalysis CDx as a companion diagnostic for Lynparza in breast cancer patients. AstraZeneca and Merck co-market Lynparza for treatment of breast cancer and ovarian cancer. 

BRACAnalysis CDx could be a significant source of growth for Myriad. Lynparza could eventually win approval for treating prostate cancer, pancreatic cancer, and other indications. If AstraZeneca and Merck pick up more approved indications for the drug, Myriad stands to benefit.

Don't write off Myriad's hereditary cancer business, either. The company launched a new product last year that could help gain market share. RiskScore helps predict the risk that a woman will develop breast cancer. The test uses clinical risk factors and genetic markers.  

Better buy

Both Opko Health and Myriad Genetics are enjoying nice rebounds and could have room to grow. I think, though, that Myriad is the better pick. In my view, the decision comes down to financial health. Opko continues to lose money, while Myriad is profitable. 

But while I think Myriad is the better choice, I don't see either of these stocks as great ones to buy right now. Myriad's shares currently trade at 26 times expected earnings. That steep valuation might be warranted if the company delivers on its potential. My preference, however, is to stay on the sidelines until there's more evidence that Myriad will be able to do so.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.