RELIABLE meaning: consistently good in quality or performance; able to be trusted.
I have found my 40 brakes to be a very reliable Lockheed style brake system.
I think that the general test is that if you can lock up the wheels and skid,you are good to go. They STOP as they were designed to with Lockheed technology of the day.
EFFICIENCY is defined as: (especially of a system or machine) achieving maximum productivity with minimum wasted effort or expense.
40 Ford brakes are not as efficient as the later Bendix system. I believe this indicates that if you had one 40 ford with Lockheed brakes and another 40 Ford with Bendix style brakes driving down the road at 30 MPH and you simultaneously apply both brake systems,the Benidix system would provide a shorter stopping distance as the Bendix system pulls the shoes tighter against the drum and requires less pedal pressure. Hence, it's more efficient.
That's why you always want to think ahead,don't tailgate and leave plenty of stopping distance with 40 brakes.
Here's an excellent discussion about your question.
https://www.fordbarn.com/forum/showt...5506&showall=1