T-Mobile (TMUS 0.47%) has transformed the U.S. wireless carrier space into an ultra-competitive arena with its Un-carrier promotions and has left Sprint (S) -- its closest competitor -- in the dust. 

As the nation's No. 3 and No. 4 carriers by subscriber numbers, T-Mobile and Sprint are locked in a battle for customers who refuse to pay the higher prices that come with Verizon Communications and AT&T's superior networks. Sprint has recently been able to slow what had been a mass exodus of customers, but it has yet to grow at the breakneck speeds T-Mobile has enjoyed quarter after quarter. 

Click on the following slideshow to find out how the two carriers performed in the most recent quarter and why T-Mobile again came out on top. 

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