well I believe the 2001FP is considered an all around better monitor, especially since you get a higher resolution and a significant addition of screen workspace (1600x1200 vs 1280x1024)
It depends upon how it is going to be used I would say. If you'd use the screens on differnce computers and the difference in price wasn't an issue, I'd say get the 2001FP
HOWEVER, if you plan on using the screens in a dual screen setup (side by side, perhaps used to extend your desktop) then you might want to consider a 2nd 1901FP. Sure, you'll have more screen space to work with if you pair up a 2001FP and 1901FP, but they wont match up (in physical size and size of the images they display. If you're not picky you might not care but depending upon who you are it might really bug you.