single triangulated is going to cause "rear steer" when the suspension flexes. if it is a double triangulated setup and it is built properly, your axle will stay perpendicular to the frame no matter how much the suspension is flexed. I built a double triangulated setup on mine and i love it. ultimately it depends on what setup will fit on your rig. Because of the frame and drivetrain setup on some vehicles you cant get a double triangulated setup to fit. FJ40's are a good example. I did alot of fabwork on a 40 for a friend. He had installed a Proffits Cruisers 4link setup which is a single triangulated setup. the lower links are basically paralell with the framerails. When the suspension flexes, the non triangulated links will pull the axle forward as the suspension droops and push the axle back when it stuffs. This causes the rear axle to "steer" or become not perpendicular to the frame. Some people dont mind this but personally i dont like it. Those are the main differences i can think of, not sure what other differences there are. Either setup will work, it just depends on preference and fitment to your vehicle.
