Each design has something going for it ,while the closed cab is warmer and dryer in rain and winter but noisier out on the road at speed and bit less head room and can be locked , the open cab has more shoulder and head room and better ventilation in the summer and in parades , it doesn't seem as noisy as there is less metal around you to bounce it off of .
To me the open cabs of all Military Vehicles just look right , the closed cabs reflect more of the civilian origins a conversation and not a purpose built design.
here's a longer ride along in a open cab CCKW Something went wrong...