The III has a better camera, it has a few features added which I will most likely never use and it fits in both my pockets just fine but also a Western Case radio pouch I happen to have on hand. (This is a very good belt pouch) fits better than the radio I bought the case for in fact.
Since I went with a contract plan (I am very happy with my service provider and plan to keep them, I might add I'm even happer now (more in a bit) the price difference was not that great after rebates.
Now, why am I happier.. Last summer I went with Virgin Mobile usb Stick, It worked, just, where I'm at now, (3g is the best it could do) it had a very small limit, it worked in another CG I park at but again only just.
Where I'm at now,, I have solid 4G with the T-moblie tower about a mile away.
The park I visit in Wilimington where teh Virgin Mobile barley worked I have solid EDGE level service
The park I spend 2/3 of my winter in I only get GPRS but... The park has great Wi-Fi so it's not a problem. (I'm only 3/4 mile from tower there too) The phone works well with the Wi-Fi for Wi-Fi calling as well. Very happy with the over all performance so far.. And though I have a data limit,, I spent almost a solid month using the phone and "Approached" the limit.. Comfortably below it.