Josh Miller/CNET

From one-upping each other on shared data plans to helping customers pen breakup letters, competition among the US' four major carriers -- AT&T, Verizon, Sprint, and T-Mobile -- is reaching new heights of aggression. But one thing we often hear from these mobile carriers is how "good" their 4G LTE networks are.

These companies either have the highest number of LTE users, the largest LTE footprint, or the most LTE devices on the market. For customers, though, the only thing that matters about LTE is how much it's going to cost them, and how fast it's going to be.

If you're looking for guidance on the former, CNET's Maggie Reardon has tons of helpful information about carrier plan pricing in her Ask Maggie advice column.

But for the latter, I recently conducted real-world data tests to get a snapshot of how fast these networks are performing. These tests were carried out in the same location, one where all carriers' 4G LTE networks are active (San Jose, Calif.), on the same weekend, and during the same times throughout the days. I executed these tests five times to calculate a fair average on the same phone, the LG G3 , with all four devices being wiped and reset beforehand, just like how you would receive them out of the box.

It's important to keep in mind that these tests are not comprehensive or exhaustive. Although I took measures to be as fair and thorough as possible, these results offer just a glimpse of the carriers' 4G LTE speeds in one place on the same device. If you're thinking about switching carriers, be sure to research how well the others perform in your particular area. And as always, let us know what you think in the reader comments below.

Average 4G LTE rates (Mbps) Download rate 40.5 32.94 3.36 38.04 Upload rate 19.81 14.63 3.02 19.36 Legend: AT&T Verizon Sprint T-Mobile Note: Longer bars indicate better performance

To first get a general idea about these networks, I used Ookla's Speedtest.net app to measure download and upload rates in megabits per second. AT&T, Verizon, and T-Mobile performed well in comparison to each other, though T-Mobile ran into one connection issue that I was able to resolve after relaunching the app. Unfortunately, Sprint fell behind the others and consistently clocked low rates at every trial.

Download times on 4G LTE for media content AT&T Verizon Sprint T-Mobile Temple Run 2 (48.61MB) 24 seconds 23 seconds 2 minutes, 38 seconds 21 seconds Riptide GP 2 (49.65 MB) 45 seconds 43 seconds 3 minutes, 20 seconds 39 seconds "The Lego Movie" (1.4GB) 6 minutes, 47 seconds 8 minutes, 5 seconds 1 hour, 8 seconds 5 minutes, 28 seconds

Next, I wanted to see how fast content could be downloaded and installed. I chose two games, Temple Run 2 and Riptide GP 2, and a full-length HD movie. T-Mobile delivered the fastest times, though not much faster than AT&T and Verizon. As for Sprint, it has two speeds: slow and super-slow. At its "fastest" it finished downloading "The Lego Movie" in about 42 minutes, and at its slowest, it took about 1 hour and 20 minutes. Clearly for this carrier, everything is not awesome.

Average load times for websites (in seconds) CNET mobile 6 6 8 7 CNET desktop 14 12 16 13 The New York Times mobile 5 4 6 5 The New York Times desktop 7 5 8 7 ESPN mobile 4 3 5 3 ESPN desktop 6 6 8 6 Legend: AT&T Verizon Sprint T-Mobile Note: Shorter bars indicate better performance

My last test was to determine how fast overall Web browsing is. I visited three sites and timed how long it took to load both their mobile and full desktop pages. All in all, Verizon has the slight edge for a faster browser experience. However, it it did stall once while loading both versions of CNET's page. In addition, while Sprint remained the slowest carrier, its delta in load times wasn't that much slower. At most, it only took 1 or 2 seconds longer than its competitors.

Again, data speeds depend on many variables, including your location and time of day. What you personally experience from these networks may differ from the results shown above. Furthermore, all carriers are working continuously to broaden and speed up their LTE coverage, so don't be surprised if these results change in the near future.