I was once told by an older and wiser scientist that you should never measure the same phenomenon with two instruments. If you do, your entire study turns into an inter-instrument comparison.
Ironically, Segal's Law, which you seem to approve of, is itself an analogy. I don't think anyone here is really concerned with knowing what time it is or whether or not it's a good idea to wear two watches.
Analogies are so powerful that you can often prove both X and not(X) simply by finding the fitting analogy.