According to an article on the website projectcbd.org, here is what they say regarding hemp vs whole plant.
We recommend CBD-rich products made using only organic, whole plant cannabis because this offers the best safety profile and superior medicinal benefits.
CBD products derived from industrial hemp potentially have several problems:
Industrial hemp typically contains far less cannabidiol than CBD-rich cannabis strains so a huge amount of industrial hemp is required to extract a small amount of CBD. This raises the risk of contaminants as hemp is a “bio-accumulator”—meaning the plant naturally drawns toxins from the soil. Hemp-derived CBD and refined CBD powder lack critical medicinal terpenes and secondary cannabinoids found in cannabis oil. These compounds interact with CBD and THC to enhance their medicinal benefits. It’s against federal law to use hemp leaves and flowers to make drug products. Hemp oil entrepreneurs attempt to sidestep this legal hurdle by dubiously claiming they extract CBD only from hemp stalk before importing it to the United States, a grey area activity at best.
Hope that helps!!