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John Legere hasn't been shy about how he views the competition. He affectionately refers to AT&T (NYSE:T) and Verizon (NYSE:VZ) as "dumb and dumber" and says AT&T ("dumber") is the biggest donator of customers to T-Mobile (NASDAQ:TMUS).

Indeed, T-Mobile has been grabbing millions of new postpaid subscribers as AT&T sees its most valuable subscribers ditch its network. But AT&T still generates tons of cash while T-Mobile only just turned free cash flow-positive. When deciding between each company's stock, investors need to weigh T-Mobile's strong growth prospects versus AT&T's steady stream of cash that it distributes to its shareholders.

Growth versus profit

T-Mobile has added over 1 million net new subscribers for 13 straight quarters, and it added more than 1 million postpaid subscribers for seven straight quarters before adding "just" 890,000 last quarter. Most of those net adds are high-value postpaid smartphone subscribers. T-Mobile's value pricing has put significant pressure on AT&T.

AT&T has lost postpaid phone subscribers in each of the past seven quarters totaling 2.9 million. However, AT&T has managed to focus more on high-value customers, increasing its average billing per customer 6.6% to $69.97 in that time. Last quarter, the company posted its best-ever U.S. wireless EBITDA margin.

AT&T is also facing competitive forces in the pay-TV market. Last quarter, the company lost 49,000 video subscribers between its U-Verse and DirecTV brands. AT&T has managed to grow DirecTV subscribers since acquiring the satellite-TV company last fall by bundling exclusive wireless services such as unlimited data. However, that growth has failed to make up for losses in U-Verse subscribers now that AT&T isn't focused on expanding the service.

AT&T is more focused on profitability than T-Mobile. With nearly 140 million wireless customers and 16 million broadband subscribers in North America, as well as 45 million TV subscribers across the U.S. and Latin America, AT&T can afford to target the most profitable customers.

T-Mobile, meanwhile, is aggressively pursuing customers by offering more value than competitors at a lower price. Its decision to zero-rate data from music and video streaming apps has its customers using around twice as much data compared with competing wireless providers. And T-Mobile's postpaid phone revenue per subscriber is about 75% of AT&T's.

One is best at what it does

While each company is effectively executing its respective strategy, T-Mobile's execution is unmatched by any of its peers, while AT&T can't say the same.

Verizon has managed to maintain its subscriber base while improving its profitability, performing better than AT&T. Over the past five years, Verizon has grown its earnings per share, free cash flow, and dividend payment faster than AT&T. Investors looking for dividend yield and growth would be better off investing in Verizon than AT&T.

However, if you're looking for a growth story and a pure play on the U.S. wireless industry, T-Mobile can't be beat. No other company is adding subscribers at even close to the rate T-Mobile is. It captured over 100% of the postpaid phone subscriber growth in the industry last year.

A look at valuation

T-Mobile's price-earnings ratio of 35.7 reflects the strong growth most analysts expect from the company going forward. Some analysts predict its earnings per share to nearly triple this year and grow another 50% next year. Comparatively, AT&T is expected to grow its earnings just 5% this year and next year. As a result, it garners a lower P/E of just 18.7. Still, given the growth prospects of each company, T-Mobile looks more attractive from a valuation standpoint. The multiple of each company for 2017 earnings expectations is 24.6 for T-Mobile and 14.3 for AT&T, putting them a bit closer on a future earnings basis.

Additionally, T-Mobile's enterprise multiple comes in significantly lower than AT&T's -- 6.5 versus 7.7. While T-Mobile is heavy on the promotions and giveaways with its various "Un-carrier" initiatives, the company expects EBITDA in the range of $9.8 billion to $10.1 billion for 2016, a 34% increase at its midpoint from $7.4 billion last year.

From both a strategic execution and a valuation standpoint, T-Mobile offers investors a better opportunity than AT&T.

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.