A structured, user-centered methodology for evaluating XR Digital Twins was developed and validated through two comprehensive validation phases and multiple user studies. The methodology integrates standardized quantitative user metrics, focusing on User Experience Quality, Task Load, Sense of Presence, Affect and Cybersickness. In addition, a Digital Twin questionnaire was created, addressing five key qualities: Enjoyment, Reliability, Information, Understanding, and Simulation. This approach was iteratively refined through both laboratory and in-the-field experiments, ensuring robustness and applicability across diverse XR Digital Twin scenarios. It provides a reliable framework for quantifying multiple user experience factors, supporting the development, benchmarking, and optimization of XR Digital Twins.