The reason air brakes became a big deal in terms of licensing is that they were killing too many people. The foot pedal in an air brake system is simply a valve. The further you push it the more air pressure it directs to the air chambers. It doesn't care if the brakes are out of adjustment and the chamber has bottomed out without applying any pressure on the shoes. To the operator the foot pedal feels exactly the same whether the brakes are adjusted right up or slacked right off. In a juice brake system the fluid is a "liquid rod" connecting the operators foot to the brakes shoes. If even just one of the brakes is out of adjustment the operater is aware of this because the pedal travel is extreme, or at the floor.
Next time you're traveling in the mountains in BC stop at one of the "Brake Check" areas at the top of a steep hill and read the instruction board. It will tell you that if you're vehicle has air brakes check and make sure they're all adjusted up. If you have hydraulic brakes, check for leaks.
Absolutely nothing wrong with a properly functioning juice brake system. The primary reason for going to air brakes is the tolerance for medium loss. Imagine having to connect hydraulic brakes to a trailer. Having to bleed the air out and ensure no leakage at all.Small amount of air loss at trailer connections is insignificant. Air brakes come with their own problems too. Condensation/moisture freezing them up, more moving parts (compressor) to worry about and far more valves and switches than a juice system.
IMHO the only reason to go to air would be if you were planning on hauling a trailer with air brakes or running an air over hydraulic trailer brake system.
Steve g.