I would get the 903 - because I expect the firmware to get better and SDK to get released. That would allow adding Xournal. However, as it stands right now, the notes feature is very poor for both 902 and 903 - it's just a smaller waste on the 902, since it has no digitizer. Note well that it's not the digitizer that's poor, it's the software use of it.
In its current state, however, I will not recommend buying it. Better to hold off for the SDK release.