My .02 cents.

Whats your purpose? You don't want people outside seeing you inside your car? or you only want heat rejection properties? If its the former go super black gray-silver-gray from solarguard, then medium charcoal up for the windshield. If its the later, go V-cool all around. Visibility will suffer on poorly lighted locations, but if there's sufficient light outside at night then there shouldn't be any problems. Its your choice.