By HD resolution screen screen did you meant the optional (not quite 1080 HD) 1680 by 1050 resolution?
The basic 1440 by 900 resolution is "HD" also by virtue of having at least 720 vertical pixels.
Both are glossy display screens.
For you and your photography is all about screen real estate. 1440 by 900 is larger than the standard 15" 1366x768 resolution but less than the 1600x900 (or optionally 1920x1080) you could get with a Dell Studio XPS 16 for example.
You could adjust the resolution of your desktop screen to see how you like the different resolutions.
Or visit a computer store and have someone demonstrate the various resolutions for you.
Thanks so much for your input! The standard screen is 1440X900 and the high resolution antiglare screen is 1680x1050. I did visit the Apple store, but it is hard to separate the "hype" from the fact.