Are you attacking air brakes? As I have used both and I like either or. You could setup an automobile to use air brakes too. Although you would need an air compressor and an air
tank. Yeah there is over 7 billion people on the planet and I think maybe 2 of them would actually buy an automobile with air brakes. No, I wouldn't be one of them. [emoji38]
So what's up with semi trucks and air brakes? Well the truck itself could use either hydraulic or air and either would work just fine. But you also have that darn trailer to worry about. Sure you could use hydraulic fluid. But making and breaking a hydraulic connection all of the time will only result in getting air into the line. I don't know about you, but I never got hydraulics and air to play well with one another. And I don't think many truckers really want to bleed the brakes every time they up connect to a trailer either. So using air instead of hydraulics solves those problems.