Warren Buffett is a stickler for consistency, and it's no surprise why. Businesses that are capable of doing the same thing year after year while still posting decent growth regardless of whatever's happening in the market and in the world tend to be winners in the long run. And for Buffett, it's no big problem to wait out decades as his investments compound in value like clockwork.

Companies like Walgreens Boots Alliance (WBA 0.74%) seem like obvious candidates for investors like Buffett. As a pharmacy and retailer, there's little it needs to do differently to keep collecting money from the millions of people who rely on its stores. But the picture is a bit more complicated than that upon closer inspection, so let's dive in.

It's a mixed bag

One of Buffett's biggest points of emphasis in investing is whether or not a business has an economic moat, and if it does, how wide. Wide moats tend to lead to robust and sturdy profit margins whether or not there are competitors in play. So they're a crucial aspect of a company's potential to make long-lived returns. In Walgreens' case, the moat consists of the locations of its retail stores, especially in high-value areas where commercial real estate may be sparse or too expensive for late-coming competitors to justify having a footprint.

But, as you may have realized, that isn't exactly a wide moat, so it isn't particularly a point in the stock's favor as far as Buffett might be concerned. Nor is Walgreens' profitability particularly durable over time; in the last 10 years, its gross margin has shrunk, and it has had a number of unprofitable periods.

Nonetheless, the company's sales grow with a consistency that would probably appeal to Buffett. Since 2002, its trailing 12-month revenue has risen by 369%, reaching more than $134.5 billion. At a minimum, that points to the enduring demand for its pharmacy goods and services.

Buffett might be pleased with Walgreens' low spending on research and development; it hasn't claimed any such expenses in the past decade. For Buffett, spending a lot on making new products or improving old ones is a sign that the company's business model may not be evergreen enough and is at risk of competition that could drive down margins.

That's not to say that Walgreens isn't changing its offerings over time to chase new growth opportunities, though. With its new plans to offer health insurance and some basic primary care services out of its branded Health Corners, it's conceivable that its growth could accelerate.

Plus, services like health insurance tend to be inconvenient to switch away from once customers are signed up, which should mean that at least some of the new revenue from selling insurance could be persistent. And health insurance is a line of business that definitely features wide and often unassailable moats thanks to the legal hurdles necessary to participate in the market. 

He'd probably like its price

So far, Walgreens doesn't have the makings of a traditional Buffett stock like Moody's or Visa, even if there are a few indications it's getting into lines of business that he might find more favorable. But there is one thing that Buffett would find very appealing compared to the company's competitors: its valuation. Take a look at this chart:

WBA PS Ratio Chart.

WBA PS Ratio data by YCharts.

As you can see, Walgreens has a significantly lower price-to-sales (P/S) ratio, price-to-earnings (P/E) ratio, and price-to-book (P/B) ratio in a head-to-head matchup against its archrival, CVS Health. That doesn't mean Buffett would be jumping to buy it, but it does mean that he'd interpret its potential for future growth as being at a discount today, which could be an important influence. 

Given that Buffett prefers to buy high-quality companies at a fair price rather than average companies at a discount, it's still hard to say that he'd be very tempted. It's not beyond the realm of possibility for that to change over the next few years, especially if the pharmacy can demonstrate that its new services are going to lead to permanent improvements to its margin.

Until then, there's no rule that says you shouldn't buy stocks that the Oracle of Omaha wouldn't be interested in, even though it's hard to justify a purchase if you use his traditional value investing framework.