I like the transflective ones for good visibility in all light conditions. I've tried transmissive ones and they were more challenging to read well in daylight.
I don't like blue for night driving but green/yellow or lower frequencies seem fine. Red should be perfect for night (except that it is a warning/alarm color).
The screen dimensions should be in the datasheets for those LCDs per your original question.
http://www.newhavendisplay.com/specs...-FSR-GBW-L.pdf
The other consideration I can think of is the backlight driver is meant for 20ma on the prebuilt, you will have to reduce the series resistor accordingly if you need it to be brighter and if you are not using a low power backlight with a current prebuilt board. The two you listed are low power (20ma) but something to consider if you are still shopping.
And speaking of ergonomics, It is far more practical to put it on the dash/in front of the instrument cluster, if you are planning on referencing it a lot. Helps keep your eyes on the road, less places to scan visually.