AT&T (NYSE:T) and Sprint (NYSE:S) are two of the biggest mobile network operators in the U.S., but they are very different companies for investors. Sprint is the low-cost provider trying to disrupt the market, while AT&T is the decades-old behemoth that's now expanding into mobile television. 

Which stock is the better buy for investors today? Here's a look at how they stack up against each other. 

Man on a mobile phone on a city street

Image source: Getty Images.

What separates AT&T and Sprint

AT&T has one of the biggest and best wireless networks in the U.S., rivaled only by Verizon (NYSE:VZ) in scale and quality. Sprint's network isn't quite as good, which everyone knows and forces Sprint to compete mostly on price. If it can't offer customers lower prices than AT&T or Verizon, it simply can't compete. 

Being the cost leader may not necessarily be a problem if it weren't for the fact that wireless companies leverage their scale to make money and have to constantly invest billions of dollars into network upgrades. And if you have lower margins than your competitors, you also have less money for upgrades. That brings us to the difference in these two companies' scale. 

A difference in scale

The chart below does a good job of showing the difference between Sprint's and AT&T's pricing power and their total assets. AT&T's sheer scale shows how much it's invested in its network advantage and the higher margin is the result. 

T Operating Margin (TTM) Chart

T Operating Margin (TTM) data by YCharts.

Sprint has chipped away at some of that advantage as 4G wireless networks have aged and the difference between networks has subsided. But that gap is about to open again. 

Building for the future

Where Sprint will have real difficulty competing is when 5G networks start to launch later this year. AT&T has said it will have 5G in at least 20 metro areas by the end of 2017, and Sprint doesn't have plans to enter the 5G market until at least late 2019. That will give AT&T a huge head start in signing up high-end customers willing to pay a premium for 5G speeds. 

Then there's the DirecTV acquisition by AT&T that allows it to offer a more complete wireless and digital service across the country. It can now bundle services together like cable companies did with TV, internet, and phone. Except this time around, all of those services will be wireless. 

AT&T is the better investment today

In telecommunications, AT&T is just a better company today. Its roomier balance sheet is a big advantage, as shown by much higher margins. And it's investing more in future technologies than Sprint has the ability to do. To top it off, the stock's dividend yields 5.1%, a nice payout for owning a company built to last in a world going more mobile every day. 

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.