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Now that AT&T Inc. (NYSE: T) and Verizon Communications Inc. (NYSE: VZ) have once again added unlimited data packages to their mobile phone plan options, this is a good time to see which of the four major nationwide mobile network companies offers the best service. T-Mobile US Inc. (NASDAQ: TMUS) and Sprint Corp. (NYSE: S) have offered unlimited data plans for some time now.

The two major criteria for measuring network performance are availability and speed: how often does a customer get a 4G/LTE signal and how strong is that signal. OpenSignal offers an app that mobile customers can download that, among other things, reports data on network availability and speed every time the customer uses the phone. The OpenSignal app sampled nearly 4.6 billion network connections in the three-month period from October 1 to December 31, 2016, and reported the results last week.

On Thursday the company released data on which of the four mobile network providers offered the best service on a regional basis. OpenSignal divided the 50 states into five regions: Northeast, Southeast, Midwest, Southwest and West.

The network provider with the best 4G/LTE availability is Verizon, which was ranked first in every region. A Verizon customer in the Midwest, for example, can expect to get an LTE connection 89.2% of the time, whereas a Sprint customer in the Southeast can expect an LTE connection about 75% of the time. Nationally, Verizon’s LTE availability averaged 88.2%, with T-Mobile ranked second at 86.6%. AT&T’s average was 82.2%, and Sprint’s was 76.8%.

On a speed basis, T-Mobile and Verizon shared the honors, with Verizon tops in the Midwest and the West and T-Mobile winning the Northeast and Southeast. The two finished in a statistical tie in the Southwest region. Verizon’s national average LTE speed was 16.9 megabits per second (Mbps) with a high of 20 Mbps in the Midwest. T-Mobile averaged 18 Mbps across three of the five regions and scored a national average of 16.7 Mbps. AT&T’s best speed was 15.2 Mbps in the Northeast (13.9 nationally) and Sprint’s best was 10.7 Mbps in the Midwest (9 Mbps nationally). Average speeds in the Southwest came in no higher than 14.4 Mbps on any network, with Sprint posting the lowest speed at 8 Mbps.

It will be interesting to see how the recent introduction of unlimited data plans by AT&T and Verizon affect both network availability and speed. Both companies will throttle connection speeds once customers reach 22 gigabytes (GB) of data in a month. Sprint allows 23 GB and T-Mobile 28 GB before putting on the brakes. All four also have 10 GB per month limits on tethering, with Sprint offering 10 GB per line and the others 10 GB total per account.