I am in fact using my N 9300 for typing longer texts and understend the need for additional keyboard. Especially since the industry has forgoten about the users as myself, and there is no smaller-than-subnotebook-larger-than-PDA-with-Keyboard devices, such as now obsolete HP Jornada 720 or NEC 900.
But, back to the subject, my advice: practice, practice, practice and you can find typing on N 9300 quite satisfying. And since you apparently don't mind the additional weight, the final answer is go N9500 for it's slightly but significantly bigger keyboard.