iPod Touch:
1. Noticably louder volume with headphones, but does not have speakers. I have no observations on iPhone's speakers.
2. Crashing is mostly a problem of the user applications, not necessarily of the OS, but I have observed less (if not even none) system crashes on my iPod than on the N800 (OS2007&OS200&).
3. I have a hardware problem with my iPod, so I have no objective observations of it's range.
4. 800x480 is a BIG plus for N800 here. Safari's multi touch navigation and zoom capabilities are certainly nice, but being able to see most sites without zooming at all is bigger advantage. Flash is not (yet) supported on the iPod/iPhone. Speedwise they appear to be roughly equal.