In 2014, Apple and Samsung were duking it out to rule the U.S. smartphone market. Samsung was selling devices with large screens, and iPhone fans were demanding a response.It took Apple some time, but the company finally released the iPhone 6, breaking with previous iterations and giving consumers a large-screen option. The iPhone won.But more than a decade later, recent smartphone sales and shipment figures signal that the Apple-Samsung fight has returned. And once again, it's all about the scr...