All the 'AN' thing is, is a standard of a fitting. Came about after the war, lots of surplus and then they have worked there way onto cars! Genuine Aeroquip has passed specific test for the 'aero' industry, hence being so expensive. The stuff from china is copy's of that, but without the tests, or quality base material.
In terms of failure, it is in general the cheaper stuff that fails. Seats have been known to crack and leak and the threads on the cheaper stuff can be poor. I personally use genuine Aeroquip on anything that is critical such as oil or fuel. Then you can cheap out on the rest. e.g i have a Chinese AN8 90 degree on the servo vacuum feed.
I think, short of using a good base material you would be pressed to improve on it. I mean the fittings are smooth internally, consistent in internal size and require no additional sealing on the threads.