They are an option , you can only use one at a time , choose the one that suits the engine of the plane you fly the most and just drop it into the samples folder and your away.....
To everyone else who is usung the UI 1.1 please hang on if your having install probs , an update is on its way , its a one folder install , no messin havin to change names and the like , keep your eye on my utube page.............
http://www.youtube.com/jafaem