new document preset resolution question

I recall hearing that one should change the screen resolution setting in the preferences located under "new document preset resolution" from the default of 72 pixels/inch to match their display properties. I'm using a 15.4" lcd set at 1280 x 800. My question is, should I leave the default setting as is, or should it be set to something higher? Additionally, could someone kindly explain how to determine the appropriate setting so that I can do this on my own in the future when I get a new display?

Thanks for your help!

could someone kindly explain how to determine the appropriate setting<<

To determine your actual screen resolution, measure the width of your display and divide the horizontal resolution by that figure.

In your case that will be (roughly) 1280/11.25 or approx 114 ppi.

(Although I can see little advantage to setting your presets to the actual screen rez other than having the rulers more nearly match real-life when viewing at 100%).