There is a HUGE difference between strains that are 20% THC and 25%-27% THC.
Yeah, its about 25% relative THC. . . .exactly the same as the difference in alcohol concentration between 80 and 100 proof whisky.
Like most drugs, effect is proportionate to dose, and that's going to be a function of not only how potent the weed it, but also how much of it you smoke. Stronger weed doesn't have any "magical" effect; it just takes less of it to get the same dose. Again, any decent grade of water hash will be >25% THC, and you could make it from any strain you like, if you're so inclined.
Not incidentally, I'm not aware of many commercial strains that will *from ceeds* consistently give you 25%+ THC, but if you could name some, I'd love to hear. (I have seen a few claims made to this effect, though I'm not sure I believe them).
With pot, the cannabinoids very widely, that's why the taste and high is so different from each strain to another. I'd much rather have my 27% THC strain with 2% CBD than a 20% THC strain with 0.8% CBD.
Well, I think that scent and flavor are mostly related to terpenes and other non-cannabinoid agents in the buds. In fact, its my understanding that pure THC actually has no discernable scent at all. Apart from some secondary potentiating effect of certain terpenes, I don't think there is any correlation between strain potency and quality of the scent/flavor (which is largely subjective anyway). You can have great tasting/smelling weed that isn't very strong, and vice versa.
I do agree with your other point entirely.
As you say, its mostly the cannabinoid
ratios that are responsible for the qualitative effect of the high. Specifically, does a strain have CBD, CBG, THCV, etc, and in what proportion are these other cannabinoids in comparison to THC. CBD, in particular has a modulating effect on THC, both reducing the intensity of the high, but increasing its duration AND changing its quality. CBG acts as a serotonin receptor agonist, and it may have anti-depressant effects, contribute to strain "sleepiness", etc.
A strain that's 27% THC/2% CBD is going to have a ratio of 13.5 THC/CBD, while the 20%/0.8% strain is only going to be 25:1 THC/CBD. The former strain would be expected to be quite a bit different in high quality than the later, and it should also offer more of the benefits associated with CBD.
Note that you should be able to get the exact same
qualitative effect with a strain that's 19% THC/1.4% CBD, but again, you'd have to smoke about 40% more of it to get the same dose.
I recently saw quite an interesting take on this. If you're interested, click on my link to "Williams Wonder" below, and go to the post on measured cannabinoids. The European company that did the measurement, "alpha-cat" has also classified different strains into "chemotypes" based on measured cannabinoid profiles, and you can get an overview of the different types, expected effects, and which cannabinoids are involved from their website. I think the reality is a little more complicated than this, because this company doesn't distinguish (for example) between otherwise similar strains with say 20:1 vs 10:1 THC:CBD ratios, but its a pretty good introduction to the concept, I think.
