I do wish we had data on primer characteristics. I am unaware of any technical data showing differences between standard and magnum primers. Data such as primer pressure curve, the mean and standard deviations, peak energy, dwell, duration of burn, amount of mass ejected, etc, etc. I was told by a guy who visited one US Army Ammunition plant that the contractors have these instrumented "mules" which measure every characteristic of the primer lot under test. However, we don't get to see that.
All we know is what we have been told in for profit magazines, and what I have read, is magnum primers are supposed to have a longer burn. Maybe they do. But how much more than a standard primer, don't know that.