AnandTech's Anand Shimpi offered perhaps the most in-depth look at both handsets. In his usual meticulous style, Shimpi describes the iPhone 5s as "quite possibly the biggest S-update we've ever seen from Apple." His take on the A7 SoC is especially telling, as it breaks down performance stats as well as an explanation of the architecture in minute detail.
The handset's camera is more of an "evolutionary" change from the unit on the iPhone 5, though there are marked enhancements in low light performance and an "excellent auto mode."
Touch ID was well implemented and Shimpi found he missed the feature when moving to the iPhone 5c.
As for the plastic-backed iPhone, Shimpi found the unit to be the "perfect replacement" for the iPhone 5, offering performance on par with the last-generation handset in a solidly constructed package. Interestingly, the 5c's display performed better in some tests than the iPhone 5s, with good contrast and color fidelity.
Walt Mossberg gives a condensed summary of his time with the iPhone 5s, touting the Touch ID fingerprint sensor as one of the phone's highlights.
"It sounds like a gimmick, but it?s a real advance, the biggest step ever in biometric authentication for everyday devices," Mossberg said.
He went on to say that iOS 7 is a "big improvement" over iOS 6, with too many new features to list. The Siri virtual assistant is more accurate and useful than before, with new voices and hooks into assets like Bing.
Mossberg's biggest complaint was the lack of change to the keyboard, as well as Apple's reluctance to allow the installation of third-party solutions as does Android.
For the iPhone 5c, Lauren Goode calls the unit a solid, premium phone. She notes the internals are largely carried over from the iPhone 5, with added improvements to LTE capabilities and minor hardware buffs like a larger front-facing camera sensor.
Goode also points out colors on the 5c's display are slightly warmer than the 5s.
While Apple has not yet disclosed the handset's battery capacity, the publication found that it lasted a bit longer under normal use when compared to similar tests on the iPhone 5.
Engadget was one of the first to put up their review of the top-end iPhone 5s once the embargo lifted on Tuesday. The publication found the handset's hardware, or more specifically the A7 SoC and camera, to be top notch. With its 64-bit architecture, the A7 may prove to be a game changer if developers get on board with software that takes advantage of the chip.
For the iPhone 5c, the publication found the handset to be "more than just the sum of its parts," noting high build quality that pairs well with the carried over equipment from the iPhone 5. The real player here is iOS 7, which delivers a great experience when combined with the colorful 5c hardware. Because no major changes were made to the phone's camera, it was found somewhat lacking. Also a bone of contention was the size of the display, which remains unchanged from the iPhone 5.
Darrell Etherington from TechCrunch said in his review that with the iPhone 5s, "Apple once again wins the right to claim the title of best smartphone available." The looks may not be different from the iPhone 5, but the internal components have a dramatic impact on day-to-day activities normal for a smartphone user. Of note, Etherington goes into detail regarding the 5s' various camera modes and improved hardware spec sheet. Touch ID is also a seamless experience that is well implemented. The A7 processor is designed for future applications, and should reach full potential down the road.
The 5c's greatest asset is arguably its new design, Etherington said. Apple's engineering gives the handset a premium feel, though not much has changed internally. Overall, the unit is a slight improvement on the iPhone 5, which Etherington believes would be the best smartphone around if Apple hadn't announced the 5s.
Jim Dalrymple took a look at both models in his writeup, saying the 5s is for those who need to have the latest and greatest, while the 5c is targeted to Android switchers and budget-minded buyers. Once again, the Touch ID feature of the iPhone 5s wowed, removing the burden of having to type in a passcode every time the phone is unlocked.
"The fingerprint sensor took all of that pain away. I still have the security I was looking for, but none of the frustration," Dalrymple writes.
Further commentary was provided on the camera upgrades, which were found to be good for every day users. Especially impressive was iOS 7's Camera app, which adds new levels of functionality with slow motion video and burst mode still image capture, among other features. Also mentioned was the A7 SoC architecture, which gives a speed boost to daily operations.
For the 5c, Dalrymple notes good build quality as one of the most outstanding features of the phone. He was impressed with Apple's ability to not only bring a lower end iPhone to market without sacrificing functionality, but actually adding features for less money.
Other notable reviews
CNET gave the iPhone 5s four out of five stars.
The New York Times' David Pogue found the new iPhones to be light on hardware advancements aside from the standout Touch ID fingerprint sensor and update camera in the 5s, but noted iOS 7 is a dramatic change for the better.
Both the iPhone 5s and 5c will be available to purchase on Friday, with the polycarbonate model already up for preorders on Apple's website, as well as those of partner carriers.