I mainly use an iPhone 6s and an iPad Pro 9.7 as my daily drivers. I notice that, on my iPad Pro, I usually see 2 out of 5 bars (see attached pic) while my iPhone 6s usually has 4 out of 5 bars. However, opening various web pages doesn't seem to show any difference in speed or quality between these two devices. Given that I know next to nothing about how the carriers work, I'd like to learn more. What do the carrier bars represent? Was I incorrect in assuming that signal strength dictates download speed?