Martin Evans wrote:the Raspberry pi causing quite a disruptive shift. I've worked with both a Beagle bone...
For sure the PI and BeagleBone are impressive. But for folks new to embedded processing, the choice of which to use: Arduino, r-PI, Beagle, etc. is not a religious question, its a real engineering choice. For hacking a prototype, the choice really makes very little difference. Both the r-PI and the BeagleBone are ARM based and run a full operating system, while the Arduino (at least before the DUE model) is a less complex CPU and runs without what is usually called an operating system.
Assuming by "PC" you mean an Intel/Amd X86 architecture machine with an operating system such as Windows, OS-X or Liniux, personally, I'd never pick a PC as the smart half to pair with an Arduino or other microcontroller. I'd use an ARM system, with as many AVR controllers as I need (and you can use a lot of them cheaply.