Having used both the Beaglebone and a Pi, I actually prefer the Pi. There is just more developer support and thinks work better. The BBB has a bunch of annoyances, like Angstrom Linux (blows), and that the on-board memory is just too damn small (2GB is not enough). Booting off of external SD works, but you have to go through this annoying contortion of holding down a button while plugging it in to make it work. Even once you get Debian booted off of the SD, it is missing stuff that the Pi has, like Google Chrome. Once you use the factory overclock option on the Pi, it is just as fast or faster too. In my benchmarks of a somewhat weird application I wrote the Pi with the standard OC (scale up to 1Ghz) was actually slightly faster than the BBB. I would overclock the BBB to make it more fair, but again there isn't the developer support and I didn't find a way to do it.
Add in that the BBB is like 60% more expensive on top of that and it's just not a good buy. If you need a bunch of PWM channels or it's far superior general I/O capabilities then yeah go for the BBB, but if you're looking for a small Linux box for more general use then the Pi is better.