Looking at this you would be best investing in a Pi. Can't help but feel these droid powered knock offs are going to be more of a headache than actual use.
I agree - go for the device that will have the largest group of users and the best support as a result. Right now that is the RPi. Higher up is the Pandaboard.
As for performance, I remember running UAE on a PII 233 back in 1998. That was before JIT and all that, and it was perfectly usable with P96. A 700MHz ARM11 should cope better (although possibly not an amazing amount better). Of course, that will require hardfile support, etc.