I would also mention that the 6000 has the brightest screen, and it is the only one that doesn't wash out in sunlight, if that is important to you.
Would you consider non-Zaurus devices? Things like the pepper pad and new Nokia devices have even bigger screens. If it doesn't have to be Linux, there are even more choices among Windows CE gadgets.
Just of of curiousity, why did you reject the Tablet PC? As far as I know, they can run standard x86 Linux distributions just like laptops.