The biggest difference between these two systems is the way organize their apps, functions, and information, so let's start here. The two interfaces largely echo the design philosophies of their host handsets' respective OSes. Carplay, like the iPhone, uses flat organizational structure that presents all of its apps and functions as large icons on a scrollable homescreen. Here, none of the functions is more than one level deep, there are no sub menus, folders or lists. Getting almost anywhere in the CarPlay interface is a one or two tap affair. It's hard to find fault with CarPlay's organization because there's not much there. In this case, simple is good.
Look at the bottom edge of Android Auto's screen and you'll see a handful of icons that provide quick shortcuts to the various functions. On one hand, this is nice because you don't have to pass though the home screen to go from choosing an audio source to looking at the map. However, all of the audio apps are siloed under a headphone icon that, when tapped twice, displays a list of cards. This sort of makes sense, as you can't really be listening to more than one audio app at a time.
CarPlay displays much less information, but there are some clever details in what it does show. For example, when you've missed a call or text message or if there's an unplayed podcast in your queue, the icon for that function will display a little red circle in its upper-right corner that contains the number of missed messages. With Google, missed message and call notifications get shuffled into the list of Google Now cards. Apple's solution seems just a tad more elegant in this respect.
Google Maps, the 800-pound gorilla of the navigation world, is the default navigation app for Android Auto. In the dashboard, the software looks even better than it does on the phone and filling the screen with well rendered maps and crisply rendered turn-by-turn directions. Along the way, Google Maps gives the driver verbal traffic updates, suggests alternate routes, and can even let the driver know if a business will be closed before the ETA.
And, depending on where you fell on the Google Now discussion earlier in this article, Android Auto also does an excellent job of integrating with Maps with its suggested destination and commute information cards.
On the CarPlay side of the divide, Apple Maps is your only choice strong contender that integrates well with CarPlay and Siri voice commands. While Apple Maps looks as good as Android's and gets the job done, most of our editors and all of the iPhone toting friends seemed to agree that Google Maps does it better. The advantage here goes to Android Auto.
Neither system gives the driver a choice to use a third-party navigation software like Waze, TomTom or Scout. This is a pity as there some really good free and paid navigation options and some excellent offline navigation options.
CarPlay keeps things real simple when it comes to messaging. It supports only Apple's own native messaging application. Text and iMessages come in as notifications and are read aloud to the driver at the touch of a button and can be replied to via Siri voice dictation. But if your friends prefer to use a different messaging app, such as WhatsApp or Skype, you're out of luck until you park the car Android Auto, on the other hand, throws the doors open and features support for integrating third party messaging apps. At the time of publication, about 11 services are supported including Google's own Hangouts, WhatsApp, Skype, ICQ, Kik and more. For sheer breadth of apps, Google takes the advantage here hands down.
Incoming messages from these third party apps are handled by Android Auto just like native SMS. Received messages are read aloud by the text-to-speech software and can be replied to via voice command. Simply tap the voice button, say "reply" and then speak your message. I found the process to be very low-distraction, requiring next to no visual input or confirmation.
Both Apple Carplay and Android Auto come out of the box swinging with extensive lists of third-party audio streaming apps. It makes sense, listening to audio content is one of the oldest and safest forms of in-car infotainment.
Obviously each system supports its respective native audio apps. For CarPlay that's iTunes Music and Podcasts. For Android Auto, it's Google Play Music. Both OSes support major players like Spotify, iHeart Radio, Stitcher, and Umano, but neither seems to count Pandora among their supported apps, the developer likely sticking to its Pandora Link connectivity which is supported by dozens of infotainment systems and car stereos.
CarPlay gains a slight advantage here with a slightly larger list of officially supported apps, which numbers 13 at time of publication versus Android Auto's 9. This could be a fleeting advantage, however. Both OSes have published APIs that allow any third-party audio app developer to easily adapt their software for Android Auto or CarPlay and new apps are almost constantly being added to either list.
Google Now's voice search component is powerful software, but so is Apple's Siri. Both allow the driver to initiate calls, send text messages, and request turn-by-turn navigation simply by speaking. Both allow the driver to effortlessly schedule reminders, make calendar appointments, and get the answer to inane questions like, "How old is the Golden Gate Bridge?"
The voice search systems are so evenly matched in my experience that I'm calling it a tie. Depending on your accent, the type of requests made and a variety of other factors, your mileage may vary.