I think it depends on how big the screens are. If you have a really big screen (like 30''), then I would imagine that wider is better. If not, those extra pixels at the bottom count more.
Also, the common choise is between 1920x1080 and 1920x1200. If those are your only choices, you get extra pixels at the bottom almost for free, they are only slightly smaller at the same diagonal. Again, with bigger screens and bigger resolutions I would imagine this matters less and width matters more.