The problem is you cannot really resolve this debate since it is very subjective. You would need to do a blind study with a large sample, and then you would need to do it across different strains to measure variability. Even if you did all this, the results could be easily debunked because of external factors (like what the smokers ate/drank, how there day was etc) could also play into how the "felt" after smoking a given strain.
I harvest at 5-10% amber (among other signs)since it had been shown that when the thc inside of trichomes begin to degrade, they turn amber. If I want couch-lock I will grow an indica.