Those "tools" often give different answers to the same questions. Clearly, at least one of them is wrong. And one is probably better than the other. Now if y

Those "tools" often give different answers to the same questions. Clearly, at least one of them is wrong. And one is probably better than the other. Now if you're tempted to use one or the other in a case by case basis, how are we supposed to choose which is best?