Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

As the markets flirt with the all-time highs we've seen recently, the Dow Jones Industrial Average (DJINDICES:^DJI) has paced this Veterans Day with modest gains so far. Even though most blue-chip stocks are trending down across the Dow Jones, the index has still picked up about 20 points near the end of trading, led by big days from Wal-Mart and IBM.

Johnson & Johnson (NYSE:JNJ) and Merck (NYSE:MRK) are doing their best to prop up health care today despite the sector's sluggish outing, but these two big pharma leaders show why not all health care giants are made equal.

Johnson & Johnson and Merck's differing paths
Johnson & Johnson and Merck both boast of huge and diverse drug portfolios. They're partners on star immunology blockbuster drug Remicade, a therapy that made $1.65 billion for Merck and nearly $5 billion for Johnson & Johnson over the first nine months of the year. Yet while Merck's stock has only climbed roughly 17.5% for the year -- a strong showing, no doubt, but one that puts it in the bottom third of the Dow Jones -- Johnson & Johnson's stock has racked up gains of more than 38% in 2013, making it among the Dow's 10 best picks year to date.

The performance of the companies' drugs have a lot to say on how these stocks are performing. Merck and Johnson & Johnson both share infectious disease-treating therapies, but Merck's failed to generate much growth out of the segment. The company's top drug in the treatment area, Isentress, has managed 6% growth this year so far to reach $1.2 billion in sales through nine months. That's no bad mark, but other infectious disease-treating drugs like Pegintron and Victrelis have struggled with slumping sales.

Johnson & Johnson's top seller in the segment, fellow HIV-fighting therapy Prezista, grew sales by 14.2% over the first nine months of the year. It also has seen revenue climb to $1.2 billion in total throughout 2013, and other infectious disease drugs, such as the fast-rising Incivo, are bolstering Johnson & Johnson's unit.

Johnson & Johnson markets hepatitis C-fighting Incivo alongside Vertex Pharmaceuticals, which labels the drug as Incivek, but it's racked up more than 34% sales growth through the first nine months of the year to reach more than $400 million in revenue. That's not blockbuster status, but it's a solid piece of Johnson & Johnson's pipeline that has experienced strong growth to keep this company moving in the right direction.

However, both Incivo and Merck's Victrelis, another hepatitis C-treating drug, will face much bigger competition than just each other in coming years. The rise of the oral hep-C therapies, led by AbbVie's as yet-unnamed therapy and Gilead Sciences' sofosbuvir, are nearing approval and will fundamentally shift this market in the future. When that happens, look for Incivo, Victrelis, and the old guard of hepatitis C treatments to feel the effects in a big way.

Fool contributor Dan Carroll has no position in any stocks mentioned. The Motley Fool recommends Gilead Sciences, Johnson & Johnson, and Vertex Pharmaceuticals. The Motley Fool owns shares of International Business Machines and Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.