Financial technology companies, also known as fintechs, have obvious appeal. Whereas traditional financial businesses -- banks or insurers, for example -- make their money by taking risks, fintechs make their money primarily by providing services for a fee. And whereas many traditional financials can only grow as fast as their balance sheets, fintechs have fewer hard limits on their growth.

Below, three Fool.com contributors explain why they see BlackLine (NASDAQ:BL), American Express (NYSE:AXP), and Moody's (NYSE:MCO) as some of the best buys among fintech stocks.

Let this accounting stock boost your bottom line

Dan Caplinger (BlackLine): Financial technology has been a high-growth area, as companies across the globe look to take advantage of the trend of moving away from cash-based transactions toward electronic payments. That's been great news for the giants of the industry in the credit card space and for up-and-coming payment processors, many of which saw strong share-price gains in 2018. But it's also opened the door to some providers of cloud-based financial services that let enterprise customers streamline operations they used to handle internally.

BlackLine is such a company, offering its clients the ability to get more from their accounting work. Rather than waiting until the ends of months, quarters, or years to gather up information and then process it into required reports, BlackLine lets its customers upload and manage data on a continuous basis. That not only reduces the crunch-time workload that deadline-based accounting methods involve, but also makes real-time information more readily available.

BlackLine's been able to grow both by bringing in new customers and by offering a wider array of services to existing clients. With close to 2,500 companies on its customer list and strong sales growth, BlackLine is just starting to come to the fore, and that makes now a good time to look more closely at the cloud-accounting specialist.

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A recent earnings miss but a great long-term trend

Matt Frankel, CFP (American Express): One fintech stock I have my eye on right now is credit card issuer American Express, which has been a staple in my portfolio for years.

First, the bad: American Express missed earnings estimates for the fourth quarter on both the top and bottom lines.

However, it's important to look past the headline numbers. American Express could be a big beneficiary as the U.S. and international markets gradually trend toward a cashless society over the coming years. Plus, the company is doing an excellent job of making new and innovative products that resonate with the crucial millennial market. This is especially true with high-end products such as the flagship $550 annual fee Platinum card, the popularity of which is a big reason why the company's card fee revenue rose 14% over the past year.

Also, keep in mind that unlike Visa and Mastercard, American Express is the lender as well as the payment processor. So if the Federal Reserve raises interest rates a couple times in 2019 as expected, American Express should see revenue rise significantly.

While some other fintech stocks offer more explosive growth potential, American Express is an excellent combination of growth potential and cheap valuation. In fact, shares trade for just 12.3 times the midpoint of its 2019 earnings guidance -- remarkably cheap for a company growing revenue at over 8% annually and one that should be a big beneficiary of several key trends over the next few decades.

Big profits from data

Jordan Wathen (Moody's): Founded in 1909, Moody's may not look like the fintech companies of Silicon Valley, but it's a fintech where it counts -- in its profitability and scalability.

Moody's makes the lion's share (roughly 85%) of its earnings as a credit ratings agency. When big companies want to borrow money, they do it by issuing bonds to the public. Prior to selling bonds, the company that wants to borrow money will get a credit rating from one or more of the big three credit rating agencies: Moody's, S&P Global, and Fitch.

Having a corporate credit rating is very important. Mutual funds, insurance companies, and banks have strict rules that limit them to purchasing certain types of bonds. For example, an investment-grade bond fund can only buy bonds that are rated Baa3 or better, a bank must set aside more capital for a junk bond than a highly rated U.S. Treasury security, and so on.

By getting a rating, companies can raise money from a greater number of institutions, which results in a more competitive interest rate. Any rational corporate borrower will pay a credit rating agency a small amount in fees to avoid a large amount of interest. There is no way around it.

But the real allure of Moody's business model is that it is almost entirely service-based, requiring very little investment to grow. Consider that in the five years since the start of 2014, Moody's has generated about $5.3 billion in cumulative free cash flow and spent only $432 million on capital expenditures. That frees Moody's to send virtually all of its earnings to shareholders in the form of dividends and stock repurchases.

Dan Caplinger has no position in any of the stocks mentioned. Jordan Wathen has no position in any of the stocks mentioned. Matthew Frankel, CFP owns shares of American Express. The Motley Fool owns shares of and recommends MA. The Motley Fool owns shares of BlackLine, Inc., Moody's, and V. The Motley Fool has a disclosure policy.