With the Kanex XD, that resolution limitation means you need to preset your video source to 720p, which potentially requires you to connect the device to another display first to lower the output resolution. Thanks to its scaler, the Belkin AV360 requires no such intermediate step. You can simply connect an external HDMI video source and the AV360 will automatically adjust the output to iMac-friendly 720p.
We can also report that the Belkin AV360 actually surpasses the Kanex XD in terms of its compatibility. Like the Kanex, the AV360 worked flawlessly with a cable box, with a PlayStation 3, and an Xbox 360 Slim. The AV360 also worked well with a Blu-ray player.
While we didn't subject it to a formal image quality test (if you're serious about Blu-ray image quality, you should be looking for a true HDTV instead of going through an iMac adapter), but casually speaking we'd say the AV360's Blu-ray image quality looked better than that of the Kanex XD. The AV360's image was crisp, while the Kanex XD seemed to lose some clarity.
We were also happy to find that the AV360 had no trouble resolving a signal from a cable box through an HDMI switcher. The Kanex XD couldn't do that. Anyone hoping to route their entire home entertainment suite through their iMac would want to use a switcher to avoid having to swap HDMI inputs. The AV360 makes that seamless, whereas the Kanex XD fails.
We went a bit further in our testing of the AV360 than in our Kanex XD review, because it occurred to us that the HDMI adapter could provide an easy way to connect the new Mac Mini or an HDMI-equipped PC to the iMac. Sadly we weren't able to make that work with either device. The Mac Mini gave us just a blank screen with the AV360. It resolved the screen of a Windows 7-based desktop for a second or two, then went black and started churning out audio static. We then doubled back and tried the same systems on the Kanex XD, with similar results. Belkin says only that it might add PC support in a future firmware update.
We don't have an Apple Cinema Display to test with the AV360, but Belkin says the AV360 will work with that display as well, and at resolutions up to 1,920 x 1,080. The AV360 will not, however, support the 27-inch iMac's native 2,550x1,440 resolution. Kanex says the Kanex XD will actually go that high. Aside from computers, which neither the AV360 nor the Kanex XD support, we can't think of many other HDMI-equipped devices that can output at such a high resolution, so we're not sure we really miss that support in the AV360. Perhaps there's a professional-quality HD camcorder or camera out there that could use it, but we suspect most consumer-oriented owners of a 27-inch iMac would happily trade 2,550x1,440 support for the ease with which the AV360 translates 1080p to 720p content on the iMac.