(WIRED) -- The iPhone 4S is available on three major carriers, leaving potential buyers to wonder whether AT&T, Verizon or Sprint is the better network choice.





Pricing plans aside, carrier quality is a significant factor in anyone's purchasing decision, and now consumers have hard data to help them choose: A just-released study reports AT&T is tops for fast data speeds, while Verizon is the most reliable when it comes to making phone calls.





Sprint's main draw is that it offers unlimited, albeit slow, data.





The study was performed by Metrico Wireless, a mobile device performance analytics firm. To test network performance, Metrico made 6,000 voice calls, conducted 8,000 data download/upload tests (both moving and stationary), and downloaded more than 21,000 web pages.





The tests found that Verizon dropped calls 2.1 percent of the time, while AT&T dropped 2.8 percent of calls and Sprint lost 3.7 percent of calls. The average dropped-call rate for the entire mobile industry is 1.4 percent. Although Sprint dropped the most calls, it had the highest call quality on the uplink (outbound calls), while AT&T had the best downlink call quality (inbound calls).





With regard to maximum data speeds, AT&T led the pack at 6,047Kbps, with Verizon a distant second at 2,371Kbps, and Sprint crawling in last with only 1,767Kbps. It's unclear, however, exactly where Metrico tested data bandwidth, and as any iPhone-toting San Francisco resident will tell you, data quality can be terrible in areas with high concentrations of tech geeks.





The original iPhone launched exclusively with AT&T, which was the sole carrier of the iPhone until Apple announced that Verizon would also begin carrying the iPhone 4 in January 2011. Prior to the launch of the iPhone 4S, rumors swirled that the phone would land on Sprint, and ultimately proved true. Of the three carriers, Sprint is the only one that provides a true unlimited data plan.





Metrico's results are consistent with what we found back when Verizon began offering the iPhone 4: AT&T offered better download speeds, while Verizon had better coverage.





Another important stat Metrico found was that the iPhone 4S performed perfectly across all three networks when it came to data task reliability. In short, 100 percent of the time, the phone was able to complete web-page loads, stationary downloads, and stationary uploads. This contrasts with an earlier Metrico study from March 2011 that found Verizon had a higher download success rate when the phone was stationary, and AT&T had a higher rate while the phone was moving.





So what's the bottom line? It looks like you're going to get a relatively positive data-downloading experience no matter which carrier you choose, if only because you will be able to download data. But if you value downloading material quickly, you should go with AT&T. If call reliability is paramount, stick with Verizon, and if you want to use a lot of data but don't care about speed, go with Sprint.





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Verizon web-page loads, stationary downloads, and stationary uploads. AT&T network performance, calls AT&T, Verizon or Sprint AT&T Verizon
question: What company dropped the least number of calls?, answer: Verizon | question: What was the phone able to complete, answer: web-page loads, stationary downloads, and stationary uploads. | question: Who led the pack in maximum data speeds?, answer: AT&T | question: What does the new study compare?, answer: network performance, | question: What does Verizon drop at least 2.1%, answer: calls | question: What did a new study compare?, answer: AT&T, Verizon or Sprint | question: Who lead the way in maximum data speeds?, answer: AT&T | question: What company dropped calls the least?, answer: Verizon