-n8xx have a much higher res screen, it's larger too, so quite useful for ebooks as well as media playback
-n8xx comes with free mapping s/w, albeit basic.
-n8xx is mostly open source, so yr not dependent on the goodwill of your vendor to crap all over your DRM controlled data.
-n8xx could connect using samba to a wireless NAS
-connect with usb host to an external hard drive and DVD rom
-n8xx can handle a bluetooth keyboard

if all you want is a media player, get an ipod - or an archos!

if you want something much more, get a nokia tablet.