The new 2017 iPhones are here, and Apple (NASDAQ:AAPL) today began taking pre-orders for the iPhone 8 and 8 Plus, which start shipping in a week. However, the company's smartphone lineup is starting to look a little overcrowded, with negligible differences among the middle-tier options.

The big new feature in the iPhone 8 is wireless charging, facilitated through a glass back and using the dominant Qi standard. Beyond that, all the device offers over the iPhone 7 are spec bumps and incremental performance gains. By contrast, the iPhone X has wireless charging as well, but also includes more meaningful upgrades such as the edge-to-edge OLED display and TrueDepth camera system.

iPhone 8, Apple Watch, and AirPods charging wirelessly

Image source: Apple.

Unfortunately, Apple has opted not to disclose much technical detail about which Qi standard it is implementing in the new iPhones. For a company that's always quick to brag about its latest and greatest product, the omission is telling in and of itself.

All signs point to an older, slower charging rate

A couple weeks before the unveiling, reports emerged that Apple might be using an older Qi standard that charges at a slower rate. Japan's Macotakara first reported that wireless charging in the new iPhones might top out at 7.5 watts, half of the most current version (1.2) that can deliver up to 15 watts of juice.

The Wireless Power Consortium that develops the Qi standard was quick to call Apple's adoption a "pivotal day for wireless charging." That's not misplaced enthusiasm, as Apple's sheer weight in the smartphone market provides powerful validation to the standard.

Apple did not specify technical details around the wireless charging rate at all during the product presentation, nor has it disclosed any detail on its site. The only clue is that both of the $60 third-party wireless charging bases (from mophie and Belkin) that Apple has since added to its online store indicate that they both top out at 7.5 watts of power. That doesn't stack up well against Samsung, which uses Qi version 1.2 for 15 watts of wireless charging in its latest devices, although it iss slightly faster than the standard 5-watt USB power adapter that Apple includes.

Meanwhile, the new iPhones are also capable of wired fast-charging using newer USB-C power adapters (starting at $74 for a 29-watt adaptor and USB-C to Lightning cable). While a welcome addition, I would still file that under the category of "modest spec bumps." That inadvertently undermines the value proposition of the iPhone 8's only real differentiating feature, leading to a meaningful trade-off: You can either charge wirelessly at a rate comparable to what you're used to, or charge wired at a dramatically faster rate (50% charge in 30 minutes) if you're willing to buy the requisite equipment.

Wireless charging in iPhone 8 doesn't sound like a particularly compelling reason to upgrade from any reasonably current iPhone, which is bad news for Apple.

Evan Niu, CFA owns shares of Apple. The Motley Fool owns shares of and recommends Apple. The Motley Fool has a disclosure policy.