JIC is good, AN is better. They are interchangeable, both 37 degree fittings, but AN has more exact tolerances, developed for military. Stands for Army-Navy. Commonly used in performance vehicles now. Brakes and fuel systems.x2 on JIC they are amazing.
Flat face oring fittings are probably about the "most reliable fittings " and don't have to be over torqued but they are metric and costly. Becoming very common on ag equipment. Cost wise and commonality of fittings makes JIC probably the best pic for this project especially if the cylinders have a npt or ORB port on them.
JIC cannot withstand pressures as high as ORFS especially when getting into larger sizesThere is absolutely no replacement for a JIC with a metal to metal taperedd seal with a minimal torque applied and they swivel too! Everytime you open an orfs fitting, you should change an o-ring! If you don't, it may leak oil all over you! JIC has no degrading parts other than long time fatigue which all metal has. O-rings have a shelf life.