If you're going for 24" or more I would go for the 1920x1200 otherwise the 1920x1080 will work just fine. There will be black bars on the top/bottom when you play movies or do other productivity applications for the 1920x1200.
Then I will go for a 1920x1080 if i change monitor. i am not sure if I want to. My current resolution is good, I think.