Look a little bit deeper under the skin.
And then look a bit deeper again past the hardware.
The thing that really differentiates the "Pi" from everything else in its hardware class is the user base and support. There have been about 400,000 Pis sold to date (last figure I saw), which compares with 300,000-odd Arduinos. Development is moving at a blistering pace. It's hard to believe they've been out for less than a year.
I've seen (and even own) dev boards with ARM SoC chips that are more capable than the Pi in terms of hardware (faster clock, more ram, more peripherals, more gpio pins), but as any Arduinoist knows, hardware without software makes an interesting conversation piece for the coffee table, or perhaps a nice paperweight.
Or to paraphrase a famous President: "It's the software (and user support base), stupid."