Touch-sensitive Navi wheel
ARM 11 369 MHz processor (40MHz more speed)
Symbian OS 9.3, Series 60 v3.2 UI (9.2 for N82)
FM transmitter
bigger battery
There isn't much difference between the two. Since N79 is a new phone, you can go for it. On paper it looks powerful than N82 and more importantly, bigger battery. My suggestion for you is to get a demo of both the phone and pick one that feels better.