I disagree that we need to pick. It's a failure to rely on a specific device in any kind of long term effort. Go for multiple hardware adaptations, one OS Core shared amongst them all and a UI on top. Applications made for the OS Core will run on those different hardwares as the applications aren't made specifically for one specific device. Start out with hardware we have (N900) and be able to move on to other devices over time by adding more hardware adaptations.