Well, if you ask what is common between Arduino, BeagleBone and Raspberry Pi, I’d say they are pretty popular in hobby market. Roger Meike has made an interesting comparison between those development platforms some time ago. We could argue that there could be more boards in the comparison list, but these are already interesting to look through.
The fact is that all three platforms are pretty mush same size (about 2”x3”). Each of them has their own benefits and shortcomings. No argue that Raspberry Pi and BeagleBone leave Arduino far behind in terms of performance, memory and connectivity. Beagle bone is a bit pricy but has an analog input what we miss in Raspberry Pi. I would say this is a bit unfair comparison, but pretty interesting read. Who knows – maybe someone will find this a useful as a selection guide of next platform.