Here’s another indoor wireless test of the iPhone 6s Plus on AT&T and the iPhone 6s on Sprint, Verizon and T-Mobile. Verizon is the fastest of the four. T-Mobile and Sprint are very slow in this speed test. LTE speeds aren’t too critical for most people at home since they’re most likely to be connected to Wi-Fi, but slow LTE speeds cause issues for some if they don’t have a home ISP. Call quality and reliability are the most important factors at home.