For much of the past five years, Gilead Sciences (NASDAQ:GILD) was a bigger biotech than Amgen (NASDAQ:AMGN) in terms of market cap. But that was before the bottom fell out for Gilead, as the stock lost half of its value from mid-2015 through the present.

Which of these biotechs is the better pick for investors now? Here's how Gilead Sciences and Amgen compare on several key criteria.

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Current products 

It's a tale of two franchises for Gilead's current product lineup. Sales for the biotech's HIV drugs are growing nicely, led by Genvoya, Descovey, and Odefsey. However, Gilead's hepatitis C virus (HCV) drugs continue to flounder, with sales tanking for Harvoni and Sovaldi. Only newer HCV drug Epclusa can claim improving sales figures. 

Gilead does have four other notable drugs outside its HIV and HCV products. Pulmonary arterial hypertension drug Letairis, angina drug Ranexa, and anti-fungal drug Ambisome are performing well, but cancer drug Zydelig has been a big disappointment. Sales for these drugs represent a small percentage of Gilead's total revenue, though. 

The picture looks better for Amgen, although total product sales fell slightly in the first quarter of 2017 compared with the prior-year period. Declining sales for autoimmune-disease drug Enbrel were largely to blame. Sales also dropped in the first quarter for anemia drug Epogen. 

On the positive side, Amgen claims a couple of products generating double-digit percentage growth -- osteoporosis drug Prolia and secondary hyperparathyroidism drug Sensipar. The company's top-selling drug, Neulasta, and bone-disease drug Xgeva had single-digit-percentage year-over-year growth in the first quarter. Cholesterol drug Repatha hasn't been a big winner yet, but Amgen hopes that its positive cardiovascular outcomes data could sway payers to loosen their purse strings. 

Pipeline

Gilead's pipeline includes nine late-stage programs and 18 phase 2 programs. Three of the late-stage programs especially stand out.

The biotech's bictegravir/F/TAF combo for treating HIV has tremendous potential and could allow Gilead to continue to dominate the HIV market. Selonsertib could be the company's first drug to treat nonalcoholic steatohepatitis (NASH), a potentially lucrative market. Filgotinib represents Gilead's best chance to enter the autoimmune-disease market.

As for the phase 2 programs, Gilead has invested significant resources in developing and acquiring additional NASH candidates. FXR agonist GS-9674 and ACC inhibitor GS-0976 could join selonsertib in treating the indication, either stand-alone or as part of combination therapies.

Amgen has 13 late-stage pipeline programs. However, nine of those are for additional indications for existing products. The biotech also has four phase 2 candidates and six biosimilars in development.

Two of Amgen's late-stage drugs are particularly interesting. Experimental heart-failure drug omecamtiv mecarbil potentially holds blockbuster sales potential if approved. Positive results for BACE inhibitor AMG520, which is being developed in partnership with Novartis, could also be huge for Amgen. However, several once-promising Alzheimer's disease drugs have crashed and burned, so AMG520's prospects are iffy at best.

Three scientists examine vials in a lab.

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Dividend

Gilead Sciences' dividend currently yields 3.08%, and the dividend is likely to increase in the future. Gilead has announced two dividend increases since initiating its dividend in 2015, and  the biotech uses less than 19% of its earnings to fund the dividend program, indicating plenty of room for further increases.

Amgen's dividend yields 2.82%. The company initiated its dividend program in 2011, and, like Gilead, has increased the dividend each year. Amgen uses around 39% of its earnings to pay out dividends, so there should be no problem for those dividend increases to continue.

Valuation

Gilead's shares trade at less than 9 times expected earnings. However, the company's earnings are expected to fall over the next few years because of its HCV franchise woes.

Meanwhile, Amgen stock trades at below 13 times expected earnings. That's relatively inexpensive, but analysts project that the biotech's earnings will grow by roughly 5.5% annually over the next few years. 

Better buy

How do Gilead and Amgen stack up in each category? Amgen gets the nod in current products. Despite Gilead's great HIV franchise, the HCV side is simply too big of a drag on revenue. Gilead, on the other hand, appears to have the better overall pipeline. Gilead also claims the better dividend and a lower valuation.

The wild card is what acquisitions these biotechs might make in the future. Both have large cash stockpiles to spend, and both need to make one or more acquisitions, in my opinion. My hunch is that Gilead is more likely to make a transformative deal, because the biotech's management really wants the company to succeed in the oncology space, an area where it hasn't performed very well thus far.

So which is the better buy? I'll go with Gilead Sciences. Sentiment is so negative about the stock right now that I believe either a major acquisition or a "string of pearls" strategy of buying smaller biotechs will help turn things around. That being said, I think Amgen should be a winner over the long run as well. 

Keith Speights owns shares of Gilead Sciences. The Motley Fool owns shares of and recommends Gilead Sciences. The Motley Fool has the following options: short June 2017 $70 calls on Gilead Sciences. The Motley Fool has a disclosure policy.