I like the concept of this thread.
silentrich is onto something with the "scale" to classify similarities. Yes it's subjective but it will show a trending value if reviewers provide their input (Is it possible to start a comparison list or summary table instead of a thread?). I understand its a math equation but fragrance x = fragrance y can be misleading. I have yet to find fragrances that are exact in the top, mid, or base notes, let alone projection and longevity.
The moment I begin to compare with the intent to substitute the real deal, I would be better getting the real deal. Now the scale would be helpful to have an idea of similar type scents if your looking to continue your bottle count or juggle cost.
I'm glad Cool Water exists as I am allergic to Creed GIT.
In fact, I have a reaction to many of the Creeds so having similar rated scents opens up options.