which monitor has better clarity a 14" or a 21"

clarity is not base on the size of your monitor. You can visit the link below if you want to understand more about LCD monitors. http://compreviews.about.com/od/multimedia/a/LCDSpecs.htm

The quality of monitors are getting better. I am using a 17" monitor too. Clarity is quite good and the view is much better than using a 14".

I have a 19" monitor and it has great clairty.

I would choose the larger one. It would be the 21 inches monitor. The larger the better. And it doesn't bring much stress on your eye.

You adjust the resolution to make the display clearer. No matter how big the screen size of the monitor or LCD you buy, it will not give a clear image if you do not set the screen resolution. See attached image. The higher the resolution value the better the picture quality. Below is a list of available resolutions. Caveat: your display/video card must be able to support the resolution before you can set it. I hope this helps. Monitor Resolution QVGA (quarter-video graphics array) 320 x 240 VGA (video graphics array) 640 x 480 WVGA (wide video graphics array) 800 x 480 SVGA (super video graphics array) 800 x 600 XGA (extended graphics array) 1024 x 768 WXGA (wide extended graphics array) 1280 x 800 WXGA+ 1440 x 900 SXGA (super extended graphics array) 1280 x 1024 SXGA+ 1400 x 1050 UXGA (ultra extended graphics array) 1600 x 1200 WSXGA+ (wide super extended graphics array) 1680 x 1050 WUXGA (wide ultra extended graphics array) 1920 x 1200 WQXGA (wide quad extended graphics array) 2560 x 1600