Epic Systems CEO Judy Faulkner and Cerner Chairman, CEO and President Neal Patterson are among the Forbes' 400 wealthiest people in America. Well-known billionaires Microsoft founder Bill Gates, Berkshire Hathaway Chairman Warren Buffett and Oracle CEO Larry Ellison take the top three positions.

[See also: Epic, Cerner reap benefits of meaningful use.]

Forbes describes both CEOs as “self-made.” Both started their companies in 1979.

Today, Cerner and Epic have the most market share of any EHR vendors, with Cerner ahead of Epic, according to a recent report from research firm KLAS.

Faulkner, 68, comes in at No. 285 on the list, with a net worth of $1.7 billion. She founded Epic Systems in 1979 in Wisconsin. Forbes pegs Epic’s 2011 revenue at $1.2 billion.

Faulkner is a member of the government's 20-member Health IT Policy Committee, which advises the Office of the National Coordinator for Health IT (ONC).

Clients include many of the country's top hospitals, Forbes names the Cleveland Clinic, Johns Hopkins, and Cedars-Sinai. Among the many health systems currently rolling out and Epic EHR, driven in part by the government’s meaningful use program, are Partners Healthcare in Boston and MaineHealth in Portland, Maine.

Neal Patterson, 62, is listed at No. 391, with a net worth of $1.12 billion. In 2011, Cerner, a public company, headquartered in Kansas City, Mo., posted $2.2 billion in sales and net income of $307 million. Over the past five years sales have grown an annualized 9 percent and earnings 22 percent.

[See also: Cerner's second quarter profit up 24 percent.]

Patterson calls himself a devoted follower of Ayn Rand, according to Forbes. According to the Cerner website, Patterson started in 1979 with a single laboratory information system.

Barry Blumenfeld, MD, CIO of Maine Health, says the health system had a very clear reason for selecting Epic in its goal to have one medical record for each patient across the system.

The reason boils down to integration. Blumenfeld believes that what gives Epic the advantage in the market.

“Long, long ago, Epic made certain decisions about the way they would build their product, and the way they would sell it," Blumenfeld says. “Where many firms: GE, McKesson, Allscripts – and others – have grown by acquisition – and they may have all the pieces. They may have an ED system. They may have a pharmacy system. They may have an impatient system, an ambulatory system. Those are really different systems. You’ve got to connect them with a bunch of interfaces. It ends up like a bunch of spaghetti. Sometimes you put M&Ms in on one side, and you get Skittles out the other end of the interface. It’s just not the same. They’re not truly intergrated."

“This is the important thing about Epic, Blumenfeld adds. “They have a single database, with a single data model. All their modules are integrated tightly. They all look and feel similar, so that if you’ve seen one, you’ve seen another. The doctors are going to see the same thing in their office as they’re going to see in the emergency room or up in the units.

Epic is "privately held," he notes. “They’ve never bought a company. They’ve never tried to integrate a bunch of products that look and act completely differently and are on different platforms and are really very hard to connect.

Many Web-based EHR companies, competitors of Epic and Cerner, criticize these firms' closed systems and client/server models as too expensive, and too clunky and complicated.

Blumenfeld has heard similar complaints. "They’ve kept it integrated, consistent," he says. "It’s not a simple system; in fact, people complain it’s a very complicated system, but everything is connected, and you can move seamlessly from one area to another without losing information or worrying, in fact, about whether there’s anything but a single source of truth."