Company: RIM (BlackBerry)
Call quality over both wireless networks was the same: decent. Voices were garbled sometimes, and we noticed an echo, just as we often did when using the phone over a regular cellular connection. Being able to make calls over Wi-Fi is a great option in areas where cellular service is spotty, though. This suggests that the RIM BlackBerry Curve 8320 was designed primarily with the US market in mind.
For both voice calls and data usage, the RIM BlackBerry Curve 8320 will default to your Wi-Fi network when it is available. Should you leave the network's range, the phone is supposed to switch your call seamlessly to the GSM network (and vice versa) - but in our tests, the experience wasn't as smooth. When we went out of range of our Wi-Fi network, calls occasionally dropped, even though cellular service was available.
Those glitches aside, the RIM BlackBerry Curve 8320 is an excellent phone. Like all BlackBerry units, it is a stellar email device, with support for 10 accounts. The included camera (which sports a flash and a 3X digital zoom) took adequate but - like many cameraphones - occasionally blurry snapshots. Among other multimedia features is an audio and video player that supports most formats (including MP3, AAC, WMA, WMV, and MP4). The player's interface is basic, but audio quality is good and video looks great. The device also has a 3.5mm headphone jack and a microSD card slot (which is inconveniently located under the phone's battery, unfortunately).
While voice quality over Wi-Fi was only passable, the capability itself is still impressive. And combined with the RIM BlackBerry Curve 8320's sleek design and awesome email handling, it makes for a winning mobile phone package.