Which Falcon is best?
Each has something unique to offer, each is enjoyable and it is very much a matter of personal preference. They are all the products of hard working people that deserve respect.
BMS, Open Falcon, Free Falcon and Allied Force are all far superior in features to the original Falcon 4 with the last original 1.08 patch.
Allied Force is the last commercial version that you will be easily able to find in stores. It is stable, good for multiplayer due to its reliability and easy to get started with.
However BMS is the most modern version with the best features and realism. It is the only version still being improved. BMS is also unique in that it supports tripleheaded displays, MFD output in all views and has extra support for cockpit builders. You can buy the original Falcon 4 from GOG.COM in the Falcon collection and then apply the BMS community addon to it.