Kit Hannah
Veteran
The last truck that I worked on had mostly SD monitors in the B unit that was being used for graphics. We had 3 HD monitors that displayed Program.
The A unit however had all HD LCD's throughout.
Some of their more expensive trucks have all HD, but realistically, all you need is SD. You're not going to get a full raster HD image until you start getting into larger monitors. You can get full 720p out of an expensive 10-12", but most everything else that is smaller will only give you 1024x768 or 800x600. I have yet to see a monitor that will do a full 1920x1080 under 15". But better signal (HD-SDI) should look better than a composite or component signal.