The new lightning port on the newer iPhones, iPads, and iPod Touch take up less space on the device allowing Apple to manufacture the newer devices thinner. An advantage of the lightning cable design is that it lets you insert the cable into your iOS device in any orientation. Unlike the standard micro-USB connector and even Apple's 30-pin port, you don't have to eye the port and line up the sides to make the cable fit.
Apple's Lightning connector also can carry up to 12W of power, which is plenty to charge either an iPhone or an iPad (when paired with an iPad 2A charger), just as you could do with the 30-pin cable. This is quite different from the micro-USB connector world of Android devices; there is no standard for conventional USB that supports more than 9W. This means complications for tablets that need 10W; either they need proprietary chargers or they charge at the 5W rate.