Good weed will have a good high.

As for when shopping to know if you have good weed; good weed will be fresh. Fresh weed will still be sticky and smell dank AF, should be scared to walk with in 50 feet of a popo because it can be smelt through a ziploc in your pocket.

Depending on how the plant is grown and the type of plant will determine how you feel while on it and that is not solely the job of THC.

Scientists have created pure THC and those who smoked it says it doesnt really do much because its missing so many other things. Things you find in many plants and fruits known as Terpenes which give flavor, aroma, and health beneifts.

I have smoked stuff with more than 80% thc such as concentrates and edibles and stuff with 20% thc or less such as regular buds or less and I actually feel more High and prefer dry herb in terms of smoking.

But to fight pain, edibles seem to be better because the effects are stronger.

The longer marijuana is exposed to air the more it dries out and the less of these compounds there are.

So in terms of health and benefit it is subjective to the type of marijuana (each strain contains different types and amounts of terpenes) and the person and how they feel on it.