Cryptocurrencies can be volatile and risky and therefore don't make great long-term investments. So, it could be a smarter idea to invest in companies that could benefit from cryptocurrencies if they continue to grow in popularity, but don't depend on them for success.

With that in mind, here's why three of our Motley Fool contributors think would-be cryptocurrency investors are better off considering American Express (NYSE:AXP), Discover Financial Services (NYSE:DFS), or Mastercard (NYSE:MA) instead.

Design of several cryptocurrency symbols.

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This payments giant could be a better investment than any cryptocurrency

Matt Frankel (American Express): Instead of investing in a cryptocurrency, the smarter approach is to invest in a business that could benefit tremendously if these digital assets continue to gain traction but that will be completely fine if they don't.

American Express is an excellent example, as the company is already experimenting with Ripple's payment technology for international transactions. The idea is that if Amex can offer cross-border transactions that are quicker and cheaper than the competition, it could be a big competitive advantage.

Cryptocurrencies aside, the company has the competitive advantage of an affluent cardholder base, with the average Amex cardholder spending about five times as much on their card as the average credit card customer. This allows the company to charge higher swipe fees to merchants. And the company's renewed emphasis on higher-end credit card products, such as its revamped Platinum Card and ultra-premium Hilton co-branded card, should keep this advantage alive.

These products aren't only keeping the company's affluent clientele around, but are bringing in tons of millennials, which are Amex's key to success going forward. In fact, nearly half of new Platinum Card accounts in 2017 were opened by millennials, driven by new and appealing benefits such as $200 in free Uber rides.

Finally, if you think that the credit card business is about as big as it's going to get, think again. American Express still has a huge market opportunity and is doing a great job of trying to capitalize on it. It estimates that there's about $34 trillion of additional spending around the world that could be taking place on cards.

Buy this bank and get a payments network for free

Jordan Wathen (Discover Financial Services): The best evidence that the payments business is an extraordinary one is how many companies (and cryptocurrencies) are trying, largely unsuccessfully, to break in. I like Discover as an investment in a highly profitable bank that just so happens to have a lucrative payments network, too.

Discover's lending capabilities were validated by the fact it sailed through the Fed's most recent stress test. Of the 34 banks tested by the Fed, it was one of eight that the Fed believes would remain profitable even in a severely adverse scenario in which unemployment soars to 10%, stock prices dive 65%, and home prices drop 30%. Though credit card loans are subject to high loss rates in economic downturns, the high yields earned on performing loans compensate for the losses.

Investors don't give Discover's network the respect it deserves, either. Discover cards are accepted in about as many places as Visa and Mastercard, and last year the company earned more than $1 billion in fee revenue related to card use, after deducting rewards paid to cardholders. 

It's my view that the market is undervaluing Discover's lending franchise (and seemingly giving no value to its payments network) given that shares trade at roughly nine times consensus earnings estimates in 2018. 

Mastering the blockchain

Dan Caplinger (Mastercard): The cryptocurrency revolution has taken the investing world by storm, and many investors are trying to find the companies that will make their fortunes by concentrating exclusively on bitcoin, Ethereum, and other popular crypto tokens. Yet with several cryptocurrencies concentrating on making payment transactions more efficient, Mastercard is an appropriate choice for a mainstream company in a position to profit greatly from advances in crypto technology.

Last October, Mastercard announced that it would start allowing some banks and merchant partners to use Mastercard's own version of blockchain technology to facilitate payments. Rather than using bitcoin or another crypto token as an intermediary, the card giant instead believes that it can develop its own parallel framework for payment facilitation. That essentially means eliminating competition at the source, and doing so early on is important in order to keep loyal customers in Mastercard's fold rather than letting them slip away to crypto-based upstarts.

Mastercard isn't the only financial company looking to use blockchain for its own ends, but it seems to be more in touch with the potential of crypto technology than some of its peers. For investors looking closely at cryptocurrencies, Mastercard's adept handling of the field makes it worth a look for those hoping to profit from technology advances in the industry.

Dan Caplinger has no position in any of the stocks mentioned. Jordan Wathen has no position in any of the stocks mentioned. Matthew Frankel owns shares of American Express. The Motley Fool owns shares of and recommends Mastercard. The Motley Fool owns shares of Visa. The Motley Fool has a disclosure policy.