My personal choice is the Schrader, but the PCL fitting seems to be very popular.. There are also Euro type fittings, one of which is fitted to the outlet from the reservoir on on my compressor, needing a hose to connect it to the filter and pressure regulator, before my Schrader outlet connection..
As already said, the different types are on interchangeable, and so short lengths of hose carrying the different types of fitting need to be made up to allow one type to be coupled to a different type.
Fittings also come in different bore to suit low or high volume requirements (such 1/4BSP or 3/8 BSP to suit different bore airlines, and air requirements of the different size air tools. You would probably have problems supplying a 1" sq drive gun with a 1/4 bore hose and fittings to obtain maximum power! )
Howard