The display size of iPhone is 3.5 inches as of now and may be it will be around it always. But the size of the Android phones has grown enormously since the past two years. It has created an impression that the screen size of 4.3 inches is quite standards. Why is this happening with Android?
Already, the explanation for the standard screen size of iPhone is given and it states that while using the handset with one hand, the thumb can reach all the corners of the screen when it is 3.5 inches. That sounds pretty cool, isn't it? Now your mind will start pondering on why this design principle is not followed by Android smartphones and on why the standard size for them is 4.3 inches.
To answer these questions, there are a couple of interesting theories. Jin Kim suggested the first one that goes like this. Google and Android OEMs first tried the 3.5 inch display with 960 x 640 and then improved the pixel format to about 1280 x 720. The operating system offers the graphics and text as Windows or OS X and so the usage of resolution over 320 ppi results in smaller UI elements so the display also had to grow to eliminate the shrinking of UI elements.
This means that, the rendering engine of Android is set in a way that if it matches the iPhone resolution then the same 3.5 inch screen will make the text and icons on the screen appear about ¼th smaller. This would result in extremely small text and also uncomfortable to focus on the on-screen tap targets. So Android is left with only one solution. Increase the display size to match the usability and resolution of iPhone and still offer the same techniques for rendering.
An alternative suggestion offered by John Gruber is that the current LTE chipsets are quite large in size and as they are power hungry, they need huge batteries. The thick smartphonesare definitely not going to fare well in the consumer market and so they have chosen to be tall and wide which results in larger displays.
But there is a small flaw in this statement. The 4 inch display Android devices have been into existence before the LTE chipsets itself. And moreover, if this was correct, the Android devices will have to shrink as the LTE chipsets grow smaller.