Also the n900 screen is 800x480 pixels vs n97 screen 640x360 pixelshttp://www.gsmarena.com/compare.php3?idPhone1=2615&idPhone2=2917
I'd say there was a pretty massive difference in the specs. The N900 has double the RAM and a way better CPU with GPU. And Maemo; Symbian s60v5 isn't very user friendly.