Leader and laggard. 

That's what you have with AbbVie (NYSE:ABBV) and Merck (NYSE:MRK) stocks, at least so far in 2017. AbbVie is enjoying one of its best years ever, with shares soaring more than 45%. Meanwhile, Merck stock is up by a single-digit percentage year to date, well below the performance for the S&P 500 index.

Investors know, however, that the past isn't nearly as important as the future. Which of these big pharma stocks is the better choice looking ahead? Here are the arguments for AbbVie and Merck.

A man, seen from behind, scratches his head as he looks at arrows pointing left and right.

Image source: Getty Images.

The case for AbbVie

You might say the investing thesis for AbbVie is as simple as H-I-J: Humira, Imbruvica, and just about any of of its pipeline candidates. Humira, of course, is not only AbbVie's top-selling drug; it's also the best-selling drug in the world. And sales continue to climb, with AbbVie reporting revenue from Humira of $8.8 billion in the first half of 2017, up 14% from the prior-year period.

There have been worries that Humira could face competition from biosimilars. Amgen (NASDAQ:AMGN) won U.S. approval for Amjevita, its biosimilar to Humira, last year. That's not as much of an issue any more, though. AbbVie and Amgen were all set to fight in court, but the companies reached a settlement. Amgen won't market Amjevita in the U.S. until 2023 and will hold off on marketing the biosimilar in Europe until October 2018. Plus, AbbVie will receive royalties on all sales of Amjevita.

While Humira remains AbbVie's biggest seller, Imbruvica claims the top spot for sales growth. In the first two quarters of 2017, the cancer drug generated revenue of nearly $1.2 billion -- a whopping 43% year-over-year jump. With additional indications potentially on the way, Imbruvica appears to be set for solid momentum for years to come.

Then there's the pipeline. AbbVie's pipeline ranks among the best in the big pharma industry. A couple of really promising candidates especially stand out. Rova-T could become another megablockbuster in oncology for AbbVie. Upadicitinib could potentially follow in Humira's footsteps in the autoimmune disease space.

One other thing to like about AbbVie (although it doesn't begin with H, I, or J) is the great dividend. AbbVie's dividend currently yields around 2.8%. The company has an outstanding track record of dividend increases and has the ability to boost the dividend more in the future.

The case for Merck

Much of Merck's appeal for investors is tied to its superstar immunotherapy, Keytruda. The cancer drug made nearly $1.5 billion in the first half of 2017, up 160% over the prior-year period. That's just the start for Keytruda, though. Although the drug has already racked up regulatory approvals for several types of cancer, Merck is evaluating Keytruda in late-stage studies for more than half a dozen other cancer indications. Keytruda should be on track to become the third best-selling cancer drug in the world by 2022, with projected annual sales of $9.5 billion.

The greatest strength for Merck outside of Keytruda is with its vaccines. Sales for HPV vaccine Gardasil jumped 30% year over year in the first six months of this year to a little over $1 billion. Several other Merck vaccines have generated solid growth as well, particularly pneumococcal vaccine Pneumovax 23 and shingles vaccine Zostavax.

Merck has also enjoyed strong growth for its hepatitis C virus (HCV) drug Zepatier, which made nearly $900 million in the first two quarters of this year. However, the company faces intense competition in the HCV arena. Merck recently chose to discontinue development of two experimental HCV drugs that were in phase 2 testing, in large part because of "consideration of the evolving marketplace and the growing number of treatment options available."

While AbbVie's dividend yield is appealing, Merck's yield of 2.85% is actually a little higher right now. The big pharma company is admittedly shelling out slightly more in dividend payments than it's earning, but there don't appear to be any reasons for investors to worry about Merck's dividend. 

Better buy

In my view, this one's a no-brainer. AbbVie is the better pick. Merck certainly has a winner with Keytruda and its vaccines, but practically every other product in the company's current lineup faces challenges. And aside from Keytruda, Merck's pipeline isn't very strong. The company recently threw in the towel on late-stage candidate anacetrapib in treating cardiovascular disease. 

AbbVie, meanwhile, appears to be in solid position for growth. I expect the company to raise its dividend again soon, which should push AbbVie ahead of Merck in that area also. Overall, AbbVie is a good pick for long-term investors on multiple fronts. I think it will remain the leader, while Merck remains the laggard. 

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