It's been three long months, but Google (GOOGL 1.50%) Maps is back on the iPhone. 

Apple (AAPL 0.15%) launched iOS 6 back in September, ditching the search giant's cartography in the process. Since then, the new service has been on the receiving end of all sorts of criticism.

Mapping dangers
The most recent instance was Australian authorities warning local motorists against using Apple Maps because it was leading some travelers astray into treacherous terrains. In characteristic fashion, frenemy Samsung immediately hopped on the storyline and set up a marketing promo in Sydney pitching its popular Galaxy S3 with "navigation you can trust."

Ironically, the search giant was also dinged Down Under with local police also warning that Google Maps could put people's lives at risk after Big G's maps have been directing heavy traffic down a small one-way road that creates a "significant safety issue."

Apple Maps has already cost two executives their jobs, most notably former iOS chief Scott Forstall. Eddy Cue, who is now in charge of Maps, also fired Richard Williamson, who was managing the Maps project.

Time and money
Google had been working to get its new Maps app for iOS out ever since getting ditched. There was concern over whether or not Apple would approve the app, but Cupertino has obviously given its stamp of approval despite risks that users will flock back to Google's familiar arms. That certainly appears to be the case, as Google Maps has quickly risen to the top of the App Store charts in less than 24 hours.

Source: Screenshot from author's iPhone.

Apple has spent hundreds of millions of dollars and several years developing its Maps service, so approving the re-entry of Google Maps couldn't be taken lightly knowing the cold reception Apple's received.

Winner by default
Despite Google Maps having some feature advantages, like public transit directions, Apple's first-party app will have the same inherent advantage it has over third-party apps of other sorts: it remains the default.

It may not sound like much, but being the default app actually goes a long way. That's why the mobile versions of Apple's Safari and Mail apps remain dominant even though there are plenty of other browser and email clients now available (like Google's Chrome and Gmail apps). For example, trying to open a link or send an email will frequently bring you right back to Apple's native apps and iOS lacks an option to redirect to a third-party choice. That may seem borderline anti-competitive, but Apple has always argued it can do this for security reasons.

Being default adds an important layer of convenience on the user level, which is why being the default search engine is also just as valuable to Google.

While Google is unable to make its Maps the default in iOS, it is doing something else that may further undermine Apple Maps. The company has announced a new Google Maps software developer kit, or SDK, for iOS that allows other developers to tap into Google Maps within their apps instead of Apple's.

Many developers frequently utilize functions like directions and other location services, so using the Google Maps SDK for iOS will reinforce its service even more.

And the winner is...
Ultimately, consumers will be the ultimate beneficiaries (the usual result of competition). Much like the YouTube app, which was also recently ditched and re-added as a third-party app, Google Maps will now receive more updates. The original iPhone Maps app interface was created by Apple, while tapping Google's data on the backend, but has languished since 2007 with few new features over the years (just like the YouTube app). Now users can look forward to regular updates and added features.

The new Google Maps also offers 3-D views and turn-by-turn navigation. The latter was reportedly one of the biggest points of contention between the two giants, as Apple wanted to offer the feature but couldn't settle on various terms. Google is also now using vector-based maps, which was one of Apple's few advantages.

Vector-based maps are more data-efficient since they automatically resize when zooming in and out. Google Maps previously had to continuously download new images when users zoomed, gobbling up more data. A study done in October showed that Apple Maps could use 80% less data than the old Google Maps in some cases. More data can translate into more fees, so users will welcome the shift to vector-based maps.

Don't be evil
For its trouble, Google is also going to finagle something important from its new Maps: data. Previously, iOS users tapped into Google Maps more or less anonymously, but now Google is requiring a Google login to use Maps. That will allow it to accumulate even more data on its users, for continued use in world domination.

iPhone users that don't already have Google accounts will need to sign up for one, further expanding Google's reach within iOS. With Android and iOS powering 90% of smartphones sold worldwide today, that's a lot of Google users.