Though investing might seem challenging at times, one of the smartest choices you can make is to focus on companies with clear-cut business advantages. Companies that offer visible advantages over their peers tend to have sustainable and growing businesses, which usually means a healthy long-term return for investors. 

What companies possess these advantages? That's a question we recently asked three of our Foolish investors. The stocks they came up with that you should strongly consider looking into include rare-disease drugmaker Alexion Pharmaceuticals (NASDAQ:ALXN), airplane manufacturing juggernaut Boeing (NYSE:BA), and search engine kingpin Alphabet (NASDAQ:GOOG)(NASDAQ:GOOGL)

A businessman fanning his cash.

Image source: Getty Images.

A rare-disease stock with major competitive advantages 

Sean Williams (Alexion Pharmaceuticals): We don't need to turn to monopolies and oligopolies to necessarily find companies that have clear-cut business advantages. Instead, rare-disease drugmaker Alexion Pharmaceuticals serves as a fine example.

Alexion Pharmaceuticals currently has three Food and Drug Administration-approved drugs in its portfolio: Soliris, Strensiq, and Kanuma. The company's focus is entirely on rare-disease drugs with ultra-orphan indications. In layman's terms, that means Alexion tries to develop drugs that treat very rare diseases. If its drugs get approved by the FDA to treat those diseases, it receives special patent protections from possible brand-name and generic competition. It's also able to pass along some very high price points to insurers and consumers to make up for its development costs. Soliris, which treats paroxysmal nocturnal hemoglobinuria and atypical uremic hemolytic syndrome, can run around $500,000 annually, making it one of the most expensive drugs in the world.

How does Alexion get away with pricing Soliris at around $500,000 a year? The answer is simple: It has little to no competition as of yet. Developing new drugs takes years and potentially hundreds of millions of dollars, and ultra-orphan indications aren't exactly on most drugmakers' radars. This means Alexion has carved out its own little niche that's given it a clear-cut business advantage.

A biotech lab researcher using a dropper.

Image source: Getty Images.

Soliris has been critical in supplying the company with healthy cash flow, enabling it to go shopping. In 2015, Alexion announced an $8.4 billion acquisition of Synageva BioPharma, giving it access to Kanuma, a lysosoamal acid-lipase deficiency drug that's designed to treat about 3,000 people in "major reimbursable markets." Thus far, Kanuma hasn't lived up to the hype, but with Soliris on track for $3.4 billion to $3.5 billion in annual sales this year, Alexion should have plenty of future cash flow to enable more rare-disease acquisitions. 

In short, Alexion's focus on rare-disease therapies has given it a clear path to financial success, and that's something investors should take note of.

5,646 is a magic number

Rich Smith (Boeing): America's biggest plane maker, and the world's, has a huge business advantage. How big is Boeing's business advantage? 5,646. 

That's how many plane orders Boeing has in backlog right now. While it may not be as big as the "over 6,800 aircraft" backlog at Airbus, it's still a lot of airplanes. At the rate Boeing has been producing and delivering planes to customers who have placed orders -- 745 planes per year -- it will take Boeing 7.5 years to work through that backlog. That means Boeing could give its sales force the better part of a decade "off," and still have plenty of business to do, plenty of work for its workers, and plenty of money pouring into its revenue stream -- should it be so inclined.

An airplane on the runway at sunset.

Image source: Getty Images.

Of course, Boeing is not so inclined. Boeing's big backlog is a huge business advantage for the company, obviating any obligation to offer customers big discounts to secure new business. But Boeing isn't resting on its laurels. Last month at the Paris Air Show, Boeing announced orders and commitments from its customers to buy 571 airplanes, worth $74.8 billion at list prices. In terms of backlog, it added more than nine months' worth of orders and commitments -- and revenues -- to its backlog in just one day.

What's more, Boeing earns a lot more profit from these revenues than does its archrival Airbus -- operating profit margins of 4.8% on its Commercial Airplanes. According to data from S&P Global Market Intelligence, that's more than a 50% premium over the 3.1% operating profit margin Airbus earns on its commercial airplanes. It's yet another huge business advantage for Boeing: A huge backlog, and a more profitable backlog as well.

Google. (Need I say more?)

Steve Symington (Alphabet): Alphabet may not be a household name just yet. But as the recently formed parent holding company for Google, as well as its various operating subsidiaries, its business advantages are apparent to even the most inexperienced investor.

For one, Google operates on a scale few other companies could dream of enjoying. Early last year, for example, Gmail surpassed one billion users, marking Google's seventh product to hit the 10-figure mark as it joined the ranks of Google Search, Android, Chrome, Maps, the Google Play Store, and YouTube. Incidentally, at VidCon 2017 last month, YouTube executives revealed that the video platform alone recently exceeded 1.5 billion logged-in monthly active users (which doesn't include those who watch YouTube videos without logging on), each of whom spends an average of more than one hour per day watching YouTube on mobile devices.

The Google logo at its London office.

Image source: Google.

Perhaps it should come as no surprise, then, that Alphabet is massively profitable and growing quickly. Revenue last quarter climbed 22.2% year over year (24% at constant currency) to $24.75 billion, helped by a 44% increase in aggregate paid clicks and 18.8% growth in Google's advertising revenue. On the bottom line, Alphabet's net income rose 29% to $5.43 billion.

Relatedly, Alphabet takes advantage of Google to fund its decidedly unprofitable "Other Bets" segment, which is primarily comprised of high-potential business that are in their pre-revenue stages. That's not to say all of Alphabet's other bets aren't proving their worth; Other Bets revenue actually climbed 47.9% year over year last quarter to $244 million, thanks to sales from Nest connected home products, Verily life sciences products, and Fiber high-speed internet. Meanwhile, Alphabet continues to plow resources into separate bets like Calico (focusing on human longevity), Google Capital (its capital investments wing), its infamous Google X "moonshot" initiatives, and its Waymo self-driving car project.

Finally, I should note that the world is doing its best to stem Alphabet's advantages. Late last month, the European Commission announced that it will impose a record $2.74 billion fine on Google over allegedly favoring its own comparison-shopping service over those of competitors as displayed in -- perhaps ironically -- Google's Search results. Google has naturally voiced its disagreement with the decision and promised to appeal. But that it must fight these battles in the first place serves as an indication of the staggering business advantage it enjoys.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.