The stingerz are really nice if you are going to move them from tarp to tarp. Or such as the case with the 11x10 jrb tarp to move them to another place on the tarp so you can make a bakers hut. Flyz are movable so you can actually take less line. I use 12' for stingers and 10' for flyz. That is because if the line is too short for a Stinger you are out of luck. But with the flyz you can move it towards the tree and gain a couple feet.
Also Flyz were the original and Stingerz look cool