Which Statistical Tool do I use?

Hi there. I have 6 experimental data sets and one control data set. I want to compare which of my experimental data set is closet to the control set. What sort of Statistical Tools should I use?
Thank you
I am solving an optimization problem and I want to see which of my experimental functions is most efficient among by six experimental function in finding the optimum solution.
Which optimization problem? Define "efficient". Again: what you are trying to achieve? What is the objective function (which you are optimizing)?