If your looking to enable OtherOS, i'd go for the teensy 2.0 ++ or any other supported board which has in excess of 64KB memory. As the guy who is working on the AsBestOS custom bootloader payload, says that it will be about 40KB, so that rules alot of the smaller boards out straight away.
However if our not looking to do so, theres np really in going for any of the boards, got a little minimus board myself