The entourage effect describes a phenomenon in which the 400+ compounds in cannabis work together to create a particular effect on the body.
For example, 100mg of isolated CBD may be substantially less effective at alleviating symptoms than 100mgs of a whole-plant, CBD-containing cannabis extract. Many argue that consuming the plant in its whole form provides all the necessary cofactors to facilitate proper absorption.
This argument is at the heart of the debate over CBD oil from hemp vs. CBD oil from cannabis.
While it may be cheaper and more cost-effective to extract CBD from industrial hemp, users may ultimately experience less benefit due to the absence of clinically significant levels of terpenes and other compounds (which occur in abundance in high-CBD marijuana).
While high-CBD cultivars of cannabis do contain much higher levels of various cannabinoids, terpenes, etc., it does not mean that there aren’t potential drawbacks to its use.
Agricultural hemp is much closer to the kind of cannabis that one would find growing naturally in the wild, whereas high-CBD marijuana is hybridized and toyed with by growers to produce the highest levels of the desirable compounds.
There is no hard science (yet!) when it comes to the theory of the entourage effect theory. It is up to each individual to decide which option is best for them.