By Joanna Stern | Photographs by Kenny Wassus/The Wall Street Journal

Let's start with the good news: The iPhone 12, the first with 5G, is indeed the fastest 5G smartphone. The speeds will knock your masks off, as we say in 2020.

Now the bad news: To see those speeds, you need to move really, really slowly. After locating your carrier's high-speed tower, stand right next to it, tap download, then freeze.

Despite being marketed as our technological savior, 5G -- the next generation of cellular connectivity -- is not a killer feature for the new iPhone 12 models. At least not in the U.S., not yet.

Don't get me wrong: The cellular speeds can be insanely fast. In some tests, it's up to 30 times faster than my home broadband. Just persuade the marketing department at MetLife Stadium -- home of New York's football teams and lots of Verizon high-speed 5G antennas -- to let you work on the field. (I did; see the video.) Just bring a power pack because 5G is a battery drain.

It's best to think of 5G as an invisible feature -- something that might one day come in handy. What makes this the best iPhone upgrade in years are a fabulous-to-hold design and substantial camera improvements.

Even those who bought iPhone 11 models last year might pine for these new ones. That said, I've aimed my testing and assessment at those who have been holding on to iPhones that are in the iPhone 8, X and XS families -- that is, phones that are two or three years old by now. And yes, I'm also talking to readers I've heard from who are still clinging to a prehistoric iPhone 6 or 7.

If you're due (or overdue) for an upgrade, opting for an iPhone 12 is a no-brainer. But to select which of the four models to get, it's best to group them together:

-- iPhone 12 Mini ($699 and up) and iPhone 12 ($799 and up): Apple's mainstream options have 5G, a new design and an improved wide camera. (They also have an ultrawide camera already found on earlier models.) The Mini has a 5.4-inch screen; the 12 has a 6.1-inch screen -- otherwise, they're identical. The Mini is available Nov. 13; the regular 12 is available Friday.

-- iPhone 12 Pro ($999 and up) and iPhone 12 Pro Max ($1,099 and up): These also have 5G but come with a slightly more premium design and a trio of cameras, including the new wide one. The iPhone 12 Pro has the same 6.1-inch screen as the iPhone 12. The Pro Max has a 6.7-inch screen, and a new telephoto camera. The Pro is available Friday; the Pro Max is available Nov. 13.

Unfortunately, because of the later ship date for the Mini and Pro Max, I was only able to test the standard 12 and 12 Pro. Meanwhile, here are your key considerations:

Aluminum or Steel?

You know that feeling when you cut your hair and it feels dramatically different for a few days? That's this year's iPhone design change. The squared-off edges, the rounded corners, the clean glass back make this the best iPhone design in years. It reminds me of a slick, grown-up iPhone 5.

I actually prefer the 12's lower-end aluminum for its lighter weight. Plus, the Pro's flashy stainless-steel frame is a fingerprint magnet.

Speaking of magnets, Apple put some in the backside of these phones so you can snap on its new MagSafe accessories. It's a neat trick -- at least in theory. The $59 leather wallet attachment is great for storing credit cards. Except a few times, when I slid it into my jeans, the magnet detached and the wallet flew off.

Then there's the $39 MagSafe charger. While it charged the dead iPhone 12 up to 50% in an hour -- faster than a typical Qi-compatible wireless charger -- Apple's 20-watt wired charger took just 28 minutes. Plus, it has a short cord and the USB-C charging brick is sold separately. In an effort to save the earth, Apple removed that from the box. Don't worry, I just reviewed some better charging options here.

Though Apple makes other MagSafe cases, you may dare to make this your first caseless iPhone in recent memory. With a new "ceramic shield" over the glass and the new flat-edge design, Apple says it has four times the drop protection. The two phones slipped off a table onto cement and both withstood the fall without any nicks or dents.

Two Cameras or Three?

The biggest decision between the 12 and 12 Pro comes down to a single camera.

Both have the same ultrawide cameras, which are great for capturing a whole scene. Both also have new wide cameras, updated with a wider aperture to let in 27% more light, according to Apple. In my low-light scene tests I could see a noticeable improvement over the iPhone 11, and big improvement over the iPhone X and iPhone 8.

So what's different? The Pro adds a telephoto camera for taking closer shots. Whenever I would switch back from the 12 Pro to the 12, I missed the flexibility of being able to zoom into a scene without disrupting the action -- a big thing for people with kids and pets.

The Pro also has a new lidar sensor, which uses lasers to capture depth information. This will improve augmented-reality apps but also enables Night Portrait Mode, photos with that nice blur around the subject, even in low light. It did a nice job, but Portrait Mode still generally struggles with tough backgrounds.

5G or Bust?

To really understand why you won't see hair-on-fire speeds when you get a new iPhone 12, you first have to know the two types of 5G in the U.S.:

Millimeter wave: "I'm going to the Verizon 5G pole, honey. Be back soon!" This is my life when testing, because the fastest 5G doesn't come to you. You go to it.

Named after its high radio frequencies, this is the blazing-fast connection Apple was bragging about during its event. In Jersey City, when testing Verizon's Ultra Wide Band network, I saw download speeds as high as 3,000 megabits per second -- 3 gigabits! That is nuts!

Yet I could only do all that when standing right next to the tower. On my stoop, a block or so away, I can manage 800 Mbps. When I'm inside, I can only get 4G. This type of 5G can't travel long distances, and obstacles like trees and walls can slow it down.

Verizon, T-Mobile and AT&T are putting up millimeter-wave cells in bigger cities and in public spots like stadiums and parks. That's why I found myself at MetLife Stadium.

Sub-6 5G: Named for frequencies under 6 GHz, this isn't as fast but provides far wider indoor and outdoor coverage. T-Mobile and AT&T have substantial sub-6 footprints; Verizon just announced what it calls "Nationwide 5G."

The issue? This sort of 5G isn't always better than 4G. Throughout the week, I saw speeds ranging from 30 Mbps to 160 Mbps on both Verizon and T-Mobile's sub-6 networks. Sometimes the iPhone 11 Pro's Verizon 4G connection would get the same speeds.

I wasn't able to test AT&T with the new iPhones yet, but in past AT&T tests with Android phones, its sub-6 network was spottier than T-Mobile's.

I did, however, see much higher speeds with these iPhones than with any 5G Android phones I've tested so far.

Even when you've got the knock-your-masks-off speed, what can you do with it?

I downloaded the first two seasons of "Breaking Bad" (about 4 GB) in less than 3.5 minutes on Netflix and Apple TV, respectively, and a 2GB game in 45 seconds from the App Store. Speedier than my home broadband network, that's for sure. Yet it took 4 minutes to pull down just one episode on Amazon Prime Video. Download time can depend as much on the service you're using as it does the speed of your network.

Plus, the iPhone 12 got uncomfortably warm during those downloads. To the point where I had to put it down.

While video streaming and FaceTime HD also looked clearer with 5G, its best use was sharing the connection with your laptop. You won't get phone speeds, but working from my laptop from the stadium, I was able to hit 400 Mbps.

Of course, there's a price for this. Literally. Verizon required me to upgrade to a top unlimited plan to get the UWB service.

And then there's the battery drain. Downloading those episodes on Verizon's UWB network used 15% of my battery. That's why Apple included a Smart Data Mode. Enabled by default, it uses only that high-speed network if it detects you need it.

Most people won't be on superfast 5G, and will find the battery life on these phones to be solid. They lasted a full day of fairly heavy use -- though fell a bit short than the iPhone 11, which consistently leaves me with at least 15% before bed time.

A lot of this is just 5G growing pains. The carriers and Apple are betting that as the networks expand, and phones get into more hands, we'll see apps and services we can't yet imagine -- just as 4G enabled the likes of Uber and Instagram.

If and when that happens, iPhone 12 owners will be ready. In the meantime, they'll have a pretty great iPhone.

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Write to Joanna Stern at joanna.stern@wsj.com

(END) Dow Jones Newswires

10-20-20 0914ET