Even if you can’t justify it logically, I can tell you that the added real estate on the 24” is very much worth the extra cost. To me, the 2005fpw felt more cramped than the 1905fp. 24” is enough that it actually allows you to do “widescreen tasks” such as having windows next to windows. You really can’t do that with the 2005fpw – the best you can achieve is WinAmp next to a window. Plus the 2405fpw has a better quality screen.
The 2405fpw is capable of displaying HD video, save for the fact that it does not have an HDCP-capable DVI. That would be a reason to wait for the 2407wfp or whatever replaces it.
Keep in mind that a few years ago, a 19” cost $700. At $824.25, you will not be disappointed with the 2405fpw.