Charlie-
Essentially your conclusion is correct, they cannot be easily converted.
Marketing and Sales has a lot to do with how companies "rate" their products. Often they use the measure that can place the product in the most favorable light (no pun intended).
For instance people often brag my flashlight has more candlepower than that one. That may be so but, it may be a lousy flashlight.
For example, how does a tight million candlepower beam, with a throw of 500 yards, uses small available batteries and fits in your pocket sound? Great huh? They make them for under $10, they are called laser pointers! Even if the beam color is white they would still be worthless as a flashlight.
For consumers it makes it very difficult to compare two lights which is why members here are asking for beamshots.
The best way of course it to use the same flashlights you are comparing in the same setting or environment.
GregR