its not about better, its just about the resolution.
1920x1080 = has an aspect ratio of 1.77, its the native resolution of HD and Blu-ray.
1920x1200 = has an aspect ratio of 1.6, its the native resolution of Widescreens.
so its not abotu which is better, its about whatever you want, no major difference between them, really...
i don't know bout which are generally cheaper or more expensive, sry...
gd luck.