The new A12 processor brings noticeably faster functionality to core features and battery life
Wired found that both FaceID and app-switching has been improved:
"Unlocking the phone with FaceID seems slightly faster. App switching feels faster. And then there are the photos."
The Verge also noticed a slight uptick in speed, but found FaceID still lacking in certain areas:
"Face ID on the XS is ever so slightly faster than the X -- just an extra beat quicker. It’s noticeable side by side, but it’s not so much faster that you won’t find yourself pointedly staring at the phone to unlock it from time to time. iOS 12 lets you add a “secondary appearance,” which allows you to set up a second person if you want, which is nice.
Other than the minor speed increase and secondary appearance support, Face ID is still Face ID: it doesn’t work in landscape or upside down or anything like that. If you wear glasses like me, you’ll still have to enter your passcode every morning when you wake up because you’re holding the phone too close to your face for it to work. And sunglasses that block IR light will still prevent it from working -- Apple says it’s working with sunglass makers to ship new kinds of sunglasses that support Face ID. (Only Apple can get another entirely different industry to adapt to its phone, instead of the other way around.)
A year later, and it’s pretty clear that Face ID is easier for people to set up and forget about than Touch ID, which means more people are securing their phones. That’s a good thing."
But they were also very impressed with battery life:
"The A12 is also the industry’s first 7nm chip to ship at scale, which is a big deal for a variety of reasons, particularly battery life. I mostly tested the XS Max, and it did great -- better than even Apple’s claim of 90 minutes more than the X. In fact, I got a full 12 hours of battery life out of the XS Max without low power mode, and that’s even under my heavy daily use of constant Slack and email usage, video watching, photo taking, and browsing. The smaller XS is rated to get 30 minutes more than the X, which has run for about 8 hours for me this past year. It’s solid."
Tom's Guide also determined both are technically faster in some key areas;
"Before we even get to the benchmark scores, it's important to note that Face ID is faster on the iPhone Xs and the iPhone Xs Max than on the iPhone X. That's because of improved algorithms in iOS 12 and the speedier A12 chip. It's just a half-second difference or so, but it's noticeable, and I appreciate being able to unlock my phone faster than on last year's iPhone X.
The iPhone Xs and the iPhone Xs Max also shined in other real-world tasks, such as video editing. It took Apple's phones just 39 seconds to transcode a 2-minute 4K clip to 1080p. The Galaxy S9 took 2:32, and the OnePlus 6 finished in 3:45.
How about opening apps? The iPhone Xs took 20.8 seconds to open Fortnite, 4.9 seconds for Pokémon Go and 6.17 seconds for the Asphalt 9 racing game. The Note 9 was slower across the board at 35 seconds, 7.2 seconds and 9.1 seconds, respectively. The older iPhone X was also slower than the iPhone Xs at 26, 7.2 and 10 seconds for the above apps."