This paper describes a methodology for quantifying the training value of extended reality (XR)-based platforms versus conventional trainers using cognitive workload and objective performance data.  The methodology was validated using low-time evaluation pilots without any prior knowledge of tactical aviation. The study involved  simulator training of air-surface (A/S) bomb delivery, and culminated in a live capstone flight for each pilot.  The study showed a statistically significantly higher situational awareness (SA) in pilots trained with the XR platform. Additionally, we observed excellent agreement between objective and subjective workload assessment which lays the foundation for workload-adaptive XR based training strategies.