FirstBuild released an infographic highlighting the differences between Raspberry Pi and Arduino.
Buy an udoo and get the best of both worlds in one board.
An Arduino is a microcontroller motherboard. A microcontroller is a simple computer that can run one program at a time, over and over again. It is very easy to use.
A Raspberry Pi is a general-purpose computer, usually with a Linux operating system, and the ability to run multiple programs. It is more complicated to use than an Arduino.