I just built a new desktop, which has the same resolution as my Sager notebook (1920x1200), except on a 24" screen (opposed to 17"). Both machines can handle the native resolutions, so I've been through your situation.
Viewing games and just text on a 17" screen at such a high resolution has spoiled my eyes - the 24" panel I have just doesn't seem as pretty or as rich as the Sager's display. I also noticed it was a heck of a lot easier to find an enemy moving or detect their helmet and barrel sticking out from a window - probably due to the area of the pixels that make the models up. On the 17" screen, the head of an enemy is a lot smaller than one on a 24" screen, and, thus, a lot harder to find. But the high-res screen with a low area just looks so good! You'll never look at a display the same way again.
If I were you, I'd choose the 1680x1050 display. 24-17 is larger than 22-19, so you won't notice so much the effect of what I did.
Plus, using a 260 on a 1440x900 display is just...wrong.