If you believe the ads run by wireless carriers, you\u2019d be convinced that nothing is more important than download speeds. There\u2019s something of an arms race going one, with each combatant trotting out evidence that it delivers \u201cblazing speed\u201d you can\u2019t do without. But it turns out you can \u2013 most of the time.\n\n\nA study of more than 28,000 users by Nielsen indicates that about half of the files downloaded on smartphones are so small (less than .05 MB) the network doesn\u2019t have time to reach those blazing speeds \u2013 and the users probably don\u2019t even notice it. What about the other half? According to Nielsen, more than 80 percent of the files are smaller than 2 MB while just\u00a0 3.9 percent are larger than 10 MB.\n\n\nHow does file size relate to speed? Nielsen explains it this way: Think of a train leaving the station. It starts out slowly, and only gradually gains momentum and speeds up. Similarly, when a user starts to download something as small as a text or as large as a video, it takes a while for the network to speed up. Small files, and remember they account for 80 percent of the traffic measured by Nielsen, have been delivered before the network is even close to its top speed.\n\n[ Also on CIO.com: How to save on mobile plans: Your guide to 16 no-contract carriers ]\n\n\u201cThe larger the file size, the longer the download, and the more time the network has to pump data faster to the mobile device,\u201d Nielsen explains. \u201cJust because a network is capable of a fast speed doesn\u2019t mean that\u2019s what consumers are actually receiving.\u201d\n\n\nThat\u2019s not to say speed is never important. Streaming video files are large, and if your carrier doesn\u2019t deliver a download speed of least 5 Mbps (the minimum recommended by Netflix for watching its videos) you\u2019ll notice stuttering and buffering. Similarly, if you\u2019re uploading really large photos, fast upload speeds are quite helpful.\n\n\nNielsen\u2019s conclusions are based on the performance of 28,259 Android phones on the LTE networks of five large carriers. Although the company didn\u2019t test iPhones, there\u2019s no reason to assume that people download larger files if their phones are made by Apple.\n\n\nNielsen\u2019s report is aimed at the carriers, but there\u2019s plenty of takeaway here for consumers. Raw speed, a big selling point, isn\u2019t the first thing to consider when you\u2019re deciding which carrier you want to use. It\u2019s important to note that speeds in the real world vary a good deal from city to city, from neighborhood to neighborhood and even from building to building.\n\n\nWhen RootMetrics, a company that conducts a huge amount of wireless testing, rated the four major carriers earlier this year, it didn\u2019t just look at speed. It considered overall quality, reliability, network speed, call quality, and data performance. You should too.\n\n\nAs Nielsen points out, video is becoming more and more important, and over time average file sizes will increase. But for now, speed shouldn\u2019t be at the top of your priority list when shopping for a new carrier.