If you want a built-in excuse for not answering that 5 p.m. email from your boss, get an iPhone 5s. With its puny 1,560-mAh battery, Apple's phone lasted a miserable 5 hours and 46 minutes on the Laptop Mag Battery Test, which consists of continuous Web surfing over 4G LTE. If you don't pick up your phone much or buy a battery case, you can make it through the day with the iPhone 5s. But why worry about it?
In contrast, Samsung equips the Galaxy S5 with a 2,800-mAh battery and a new Ultra Power Saving Mode that turns the settings down when you're running low on juice. Samsung also provides a removable back panel that lets you replace its battery, either with a spare of the same size or a third-party extended battery.