Why?
1920x1200 is higher resolution, including more vertical space, which is great for internet use and productivity. I'd always go for the higher res if you have a choice. The reason the black bars are there is because those are all of the pixels that you wouldn't have if you had a 1920x1080 screen. So, while you're watching HD movies, you've effectively got 1920x1080 anyways, but for everything else, you have an extra 230,400 pixels to play with.