In this paper extremal values of the difference between several graph invariants related to the metric dimension are studied: mixed metric dimension, edge metric dimension and strong metric dimension. These non-trivial extremal values are computed over all connected graphs of given order. To obtain such extremal values several techniques are developed. They use functions related to metric dimension graph invariants to obtain lower and/or upper bounds on these extremal values and exact computations when restricting to some specific families of graphs.