At the end it depends on what you expect:
- you want to “compare” certain lights on similar levels? Then it might be ok
- you want to “measure”? Then all of the described models are just crap
After studying all the different models, the possibilities and limits, you will get a different view on all the “measurements” that some people take as “defined”…
But as I said: if you want to compare, it will be good enough.