FORTUNE -- Last Friday, while waiting for dim sum with a friend at a neighborhood haunt in San Francisco, I whipped out the gold iPhone 5S I had on loan from Apple (aapl). I waved it around, like someone who just got engaged might exaggeratedly wag their ring finger for attention. When that didn't work, I loudly demonstrated to my friend how the device's fingerprint scanner worked.
That's when the couple next to us perked up. They stared at the phone, then back to me with looks of bitterness and jealousy. "We waited three hours this morning at the Emeryville store," griped the woman, who had hoped to buy a gold 5S with her boyfriend but struck out: the Apple store only had a few of them.
Throughout dinner, the pair glanced at the 5S on our table, longing for a device seemingly as precious as gold itself. Why they wanted it, of course, is a matter of personal preference. But there's no denying that in the six years of the iPhone's life, the device has become a highly coveted status symbol: The owner with the newest model during those first few weeks becomes a kind of transient trendsetter, someone worth envying to those who must wait weeks or months until their own devices arrive.
By now, the Apple faithful know that when the letter "S" trails the name of a new iPhone, it will look a lot like last year's model. The iPhone 5S doesn't buck that formula, but it does toss in enough new tweaks to warrant what Apple has called "incredible demand." (It's already backordered through October.) The subtle champagne-hued gold, a new addition that joins the iPhone 5S's space gray and silver, is enough to alert keen, nearby observers that the user possesses Apple's latest. Other than that, the 5S looks almost exactly like last year's light and svelte 5, from the size of that 4-inch Retina display to the two-tone glass and aluminum back. It also weighs the same 3.95 ounces.
More has changed on the inside. At its product announcement earlier this month, Apple played up its new A7 processor, one of the first smartphones to run on 64-bit architecture. While Apple has said the A7 offers twice the speed as its predecessor, it also allows for more data to be crunched at once. For now, that mostly translates to faster app launches and smoother animation -- both were noticeable from the get-go -- inside the new iOS7, a radical revamp of the mobile operating system that ditches the previous skeuomorphic look for one that's flatter and cleaner. (Although the software team clearly had a lot of fun with sweeping transitions and animations: apps, screens, and messages swoop, zoom, and bounce quite liberally.) In the long run, the A7 will translate into more complex apps from developers and, ideally, better user experiences.
Fingerprint scanning has also found its way into the 5S with Touch ID, a nifty piece of tech that's the result of the $356 million acquisition of AuthenTec last year. Touch ID is built right into the phone's home button, now surrounded by a matching metallic ring. Setting it up so the scanner recognizes your fingerprint is a one-time deal that takes two minutes, but it's actually a pretty entertaining process. And for what it's worth, Touch ID also appears pretty secure, too: at least 10 people I approached couldn't get into my phone because Touch ID didn't recognize their prints. With enough time, the right tools, and money, it's of course possible to hack, but it's not easy. ("It's your phone -- we're not launching missiles here," Bruce Schneier, a security technologist, told Fortune. "We're looking for a little bit of security, and I think Touch ID is a really great idea for that.")
As for the camera, Apple has slightly improved that, too. It's still 8 megapixels, but the company says the slightly larger sensor and aperture should make for better-looking low-light shots. I didn't notice a major improvement on that front, but I saw somewhat more detail in stills. When I used the 5S's new two-tone flash -- two LEDs instead of one -- the results were more dramatic: Skin appeared more natural, colors more accurate. That a flash was used is obvious, but the results were less "washed out."
For iPhone 4 and 4S owners, upgrading to the 5S will seem like a huge improvement given that iOS7 on the new model is a smooth experience. For them, upgrading is a no-brainer. iPhone 5 users, however, can afford to wait until 2014. The 5S doesn't currently offer a huge improvement in performance that users can feel, but that will likely change as iOS7 evolves and developers update their software to take advantage of that A7 chip.
Starting at $99 in five bright, candy-colored shades and six equally vibrant silicone cases, Apple's goal with the iPhone 5C seems obvious: retain its reputation as an arbiter of luxe gadgets yet appeal to the younger set and markets with generally smaller disposable incomes.
Unlike its high-brow glass and aluminum sibling, the 5C is "unapologetically plastic." Put simply, it's an iPhone 5 with a plastic black. And while I don't personally care for most of the color options Apple opted for, the 5C is a pleasure in hand. Curved at the edges, the smooth, lacquered plastic is more ergonomic than the harder edges of the 5S. A steel-reinforced frame also means it feels extremely solid -- there's no flexing of materials anywhere on the device, no matter how hard you grip. Likewise, the firm plastic buttons all click satisfyingly. In other words, plastic the 5C may be, but it doesn't feel cheap.
Still, it does feel decidedly less premium, not just because of the plastic but because it also shares just about all of the same features with last year's model, from the A6 processor to the 8 megapixel camera. Where the 5C edges out its older sibling is in its slightly better front-facing camera and longer-lasting battery. The latter should net users another one to two hours of talk time, or roughly the same as what I saw on the 5S.
Apps don't quite zip like they do on Apple's flagship smartphone, but the 5C generally runs iOS7 well. The biggest difference may be with games like Infinity Blade III, which takes advantage of the 5S's processor. On the 5C, the game runs well enough, but on the 5S, the action is smoother and things look sharper.
The iPhone 5C is a perfectly capable device -- it's just not a new one. This is likely why in the U.S., the 5S is backordered while the 5C remains easy-to-find. Apple has the right idea in catering to two different markets. But even so, the year of the iPhone 5S still feels like an interim period of incremental upgrades. Next year, with the iPhone 6, presumably with an all-new design, Apple's new dichotomy of high-end vs. "budget" should become much more interesting.