This depends on what sort of question you are asking about the third data set. It sounds like you are saying something like: I have 5 points of data collected from running a system, and two models of the system, and I want to determine the accuracy of each model at predicting system parameters. Is that what you are trying to do?

@john Allen

yes that's exactly what I am asking for

There isn't any meaningful statistical test you can do. I would just graph the data comparing the three.