If you own an iPhone and a Mac, Apple's new system for connecting the two is one of the best new features for OS X 10.10 Yosemite. True, Apple is years behind Google when it comes to making and taking phone calls from the computer, but its better-late-than-never approach gives the company two big advantages over Google's system: the fact that it easily syncs with your phone, and that it's part of a tightly-integrated system that goes beyond making calls.
How it works
So long as your iPhone and Mac with OS X Yosemite share a Wi-Fi network, you'll be able to take calls on your computer that come to your phone -- you can mute audio, and also switch to video mode.
The feature lets you dial out as well, say, by clicking a number that's stored in your address book, calendar, messaging app, or Safari browser -- a restaurant or store's phone number, for instance. As an added bonus, Apple has given the calling feature enough smarts to automatically enter a passcode when you're dialing into a conference line.
How it's different from Google Hangouts and Google Voice
Google has two different methods for making calls from your computer. First, there's Hangouts, which overrode the erstwhile Google Talk application with a peer-to-peer messaging app that also supports voice and video chats with other Hangouts users over VoIP.
You can make Hangouts calls to outside lines, but you'll have to buy credit, just as you would with Skype, and your caller won't be able to identify your call or return it through a fixed number that belongs only to you. In fact, Hangout calls are marked as originating from an unknown caller.
The second option through Google's system is to link your Gmail account to Google Voice, which I personally use. With Google Voice, it doesn't matter which phone you use or if you're on a Wi-Fi network at all. However, Google Voice account ownership has its own ups and downs, and the service is limited to the US, its largest limitation by far.
How useful will Mac calling really be?
How often you use Mac calling between OS X Yosemite and your iPhone really depends on how you use your rig, and how many calls you generate and receive.
Apple's official example is that you can answer calls on your laptop or desktop while your phone is charging in the other room. That's a perfectly good use case, and as a Google Voice user whose incoming call notifications pop up on my desktop at work, here's another one: sometimes alerts that appear in front of your eyes are easier to notice and respond to than one on a tiny screen at your elbow.
If I'm already looking right at the screen when a call comes in, I occasionally take calls through the computer -- it keeps my concentration and gaze focused and keeps my hands on the mouse, not fiddling with the phone's controls.
That's when I'm at home. At the office, I generally see (and hear) the on-screen call notification before I see my (silent) ringtone alert. As a cubical-dweller in an open floor plan, I don't take many personal calls at my desk. That Google Voice popup helps me make the decision to either walk away with my phone somewhere more private, or table the call for later. A pair of headphones with a built-in mic could also do the trick for semi-private conversations.
In addition to taking calls, Yosemite supports click-to-call to dial out. As with the iPhone, clicking the screen to enter a personal or business number will certainly save you a step from reaching for the phone and typing in numbers you see on the screen.
One drawback with the current version of Yosemite (beta, released to developers) is that it doesn't include a dialer for punching in one-off numbers you don't find online or in your contacts list -- say you'd like to enter a number from a business card, or punch in a number you know by heart without first trawling through the address book.
Apple's on-screen calling is a convenience, but it's only one part of a larger push to bridge your iPhone (and iPad) with the Mac. A concept that Apple calls Continuity and a technical protocol called Handoff also make it possible to share all sorts of content between devices, including documents and messaging conversations. It's also part of the schema that lets your Mac draw a hotspot data connection from an iPhone.
My colleague Jason Parker describes Handoff in detail here.
What it means to Mac owners, and competitors
I'm guessing I'm in a minority of Mac users who also uses Google Voice with Gmail to field incoming calls, but once my MacBook Air updates to Yosemite, I'll instantly, and automatically join a much larger community of Mac-and-iPhone owners who can start using roughly the same features without even thinking about it.
This deep integration, without tinkering with settings or signing up for extra accounts, is what makes Mac calling most compelling, in the same way that Apple managed to make FaceTime seem like a revelation for a lot of casual users who weren't familiar with other mobile video chat services.
Since Mac calling is just one example of Apple's expanded relationship between the iPhone and the computer, Apple is essentially training its users of both products to start relying on this convergence of computing power.
For users, this means fluidly moving between devices for content and calls. For competitors, like Google, it means that Apple's in-house services could give its ecosystem the home-court advantage over third-party solutions, just by the very presence of a dialog box that appears in the corner of your screen when someone calls your phone.