The iPhone 4 design and specifications have changed significantly from the iPhone 3G. It’s form is now rectilinear and looks more masculine compared to the iPhone 3G smooth pebble look.
It now includes a front facing 3 megapixel camera and 5 megapixel with auto focus and an LED flash at the back. Included in an iOS 4 software update is the HDR function.
What it does is take two quick successive photos at two different exposures and combines it together. It results is nicer photos where there is a large contrast, the areas in shadow would otherwise be lost.
In fact, I hardly used my Olympus Pen EP 1 during a short trip. The iPhone 4 was smaller and easier to whip out and capture the shot.
Another area I found to have improved was the GPS chip. It could possibly be due to a faster processor and more memory. Using the Tom Tom navigation app, the iPhone 4 was the fastest to lock on the location. It also tracked the position more accurately and kept up even when making lots of turns.
For users on the original iPhone or iPhone 3G, I would recommend upgrading to the iPhone 4. However, users of the iPhone 3GS might want to hold out for the next version especially for those still locked in a contract with their mobile operator.
The iPhone 3GS is compatible with the iOS 4 upgrade and supports useful functions such as multi tasking and folders. Users like myself who upgraded the iPhone 3G to iOS 4 will be frustrated with a very slow interface and possible faulty wifi. So leave that iPhone 3G alone on iOS 3 and get the iPhone 4 if you really want to extra features in iOS 4.