Since June 2007, Apple has decided to use the same Screen size for iPhone and iPod Touch although the competition installed bigger sized display screens. Many people around the world wondered: why Apple sticks with the 3.5"? Maybe for keeping the whole phone size low, maybe for DPI(dots per inch) considerations, maybe because of hardware limitations.

There is no official press release statement about this subject but the real reason for the 3.5" screen size  is the iPhone's handling using one hand. The average sized thumb can't reach all the corners of a 4" screen unless the phone is very slim or the display is edge-to-edge. So maybe this is the future for iPhone 5.

The pictures below indicate the area that can be touched with the thumb while holding some of the biggest sized phones in the left hand:

iPhone 4s: 3.5" inch screen size

Google Galaxy Nexus: 4.65" inch screen size

Sony Ericsson Xperia Arc S: 4.2" inch screen size

Samsung Galaxy S II: 4.3" inch screen size

HTC Sensation XL: 4.7" inch screen size

Motorola Droid/Milestone 3: 4" inch screen size

Although I'm sure they'll find the perfect solution, it will be very interesting to see what screen size will be used for the iPhone 5. It's hard to believe that Apple will remain conservative and the competitors go bigger and bigger.