The team at 9to5Mac managed to get their hands on a 2015 Hyundai Sonata, a car that's particularly special in its ability to run both Android Auto and Apple CarPlay side-by-side. Thankfully, they did what every good gadgeteer should with the opportunity: an extensive comparison video.
On the surface, both systems seem relatively similar: you plug your phone into the dash with a regular charging cable, and then the phone powers a simplified screen on the dash, letting you do things like read notifications, reply to texts, dial numbers, and do navigation. They both also rely extensively on voice control to try and minimize the number of reds you run.
One of the main differences comes in the home-screen setup: Android Auto doesn't have one, relying instead on Google Now as the focal point of the system. With CarPlay, you get a very familiar-looking row of icons instead.
Both Android Auto and CarPlay are available now -- assuming, of course, that you're buying a brand-new 2015-model car from one of the manufacturers offering connected car services. If not, your best option is probably Pioneer, who offer CarPlay (and hopefully Android Auto in the future) on their NEX in-dash systems, available as an aftermarket option from upwards of $US700. [9to5Mac]