Nothing bad will happen, they install differently (WOAI adds a separate traffic.bgl for each package, and PAI creates a traffic.bgl which cumulatively adds further flightplans to it). Only thing to consider is that it wouldn't be recommended to run two similar airlines from both sources as you would likely have many duplicate AI flights, or just too much AI period. Each has packages that are not available from the other, so why not be open to both.