Resolution in games

Bigger can not be equated with either quality or resolution. For example, HD (1920 x 1080) resolutions can be found on screen sized from 13" to 27"

http://en.wikipedia.org/wiki/Dot_pitch

The following 3 columns are for a screen showing 1920 x 1080 resolution:

Sreen Size Dot pitch and Pixels per inch

13.1 0.151 168.2
15.6 0.180 141.2
16.4 0.189 134.3
21.5 0.248 102.5
23.0 0.265 95.8
23.6 0.272 93.3
24.0 0.277 91.8
24.6 0.284 89.6
27.0 0.311 81.6

http://thirdculture.com/joel/shumi/computer/hardware/pp...

Your screen has 84.43 pixels per inch, your friend's is at 99.89

The pixels per inch or "dots per inch" is an indicator of how clear the image will be. Anything under 96 or so will appear "grainy" to the average human eye as you can see the individual dots on screen. The more pixels per inch the "sharper" the image will appear and the more expensive (all other things being equal) the monitor will be.