The difference between several screen sizes of mobile devices have always been a wonder to me. I use a 5.3 inch device and when compared with a 7 inch device, it still looks small. Here is an excerpt from a Quezi question explaining how screen size is measured:
The size of a mobile phone display or of a computer monitor is given by a single length in millimeters, centimeters or inches. This measurement is taken diagonally, so it gives the largest straight-line measurement that can be obtained from the display. The quoted screen size, being a diagonal, is larger than the height or the width of the display.
Read more about how screen size and aspect ratios are measured on the Quezi question page.
I get the fact that screen sizes are measured diagonally but what I cannot seem to get is how astronomically different a 7 inch device is from a 10 inch device for example. Afterall, two Samsung Galaxy Notes do not make a Galaxy Tab 10.1 (in size that is).
Perhaps you can weigh in your views on differences between screen sizes.