The quick disconnects with 1/4"" barbed fittings are pretty straight forward. You connect them to your liquid or gas tubing by clamping them down with an ear (5183, 5184, 5179) or SS tubing clamp (5182) as a more permanent, single purpose use. The threaded fittings and barbed swivel nuts allow for more options. At the simplest level, these are easier to work with when your tubing gets twisted around as the barbed swivel nuts will rotate.
If you go with a threaded gas fitting, you can get a better fit onto the 5/16" gas tubing by using a 5/16" barbed swivel nut (5187). Also, the threaded gas quick disconnect will screw into the compact CO2 injector (5110C).
Using liquid threaded quick disconnects with liquid tubing outfitted with 1/4"" barbed swivel nuts allow some increased functionality like constructing a keg to keg "jumper cable" for transferring cleaner, sanitizer, or beer between kegs, pushing with CO2.
Threaded disconnects are also useful for switching beer and gas serving lines around to counter-pressure bottle fillers (5325, 5327F) or creating a compact chrome faucet along with parts 5113 and 5360. As you can see, the threaded connectors allow for all sorts of extra functions and possibilities for your kegging system!"