To be frank, price. I'm a student so just about anything over $400 is $400 too much at the moment. I actually intended the item to be a stopgap, between now and when I start university in Japan in september, when I'll be able to get something more suitable to my needs. However as all the japanese zaurii have built in kanji recognition, which is not supported at all on the western ones (?), this put them far above the usual denshi jisho machines. But due to the change in price of the other models I'd be far better off considering a canon word-tank, than any of the later SLs since the dictionaries provided are far superior to even the comericially released electronic dictionaries for other platforms, such as Eijiro. And buy two denshis one with a specific kanji recogntion ability. I wanted a Zaurus because I know it would be far more flexible, but for the amount of the later ones, again, I could find something better suited for my needs in Japan.
I hope that made sense