When used correctly, Rue is more of a truth serum / diagnostic tool, whereas caapi is a mystical gateway.
Both feel like the foundation of any potion meant to open the doors to Spirit.
Rue is more Divine/Upperworld associated, Caapi more general Spirit.
Both, when used correctly are bridges to the plant world and all plant spirits.
Rue has more of a "home" feeling and inspires love and connection with loved ones, whereas Caapi feels like a wild jungle.
Both are nootropic and especially together with DMT, open the doors of knowledge, activate the dormant faculties of learning.
Caapi carries the spirit of the Amazon, rue carries the spirit of whichever desert or steppe it was harvested from.
Edit: my perception of rue is skewed to the certain strain I am allied with. It is compassionate and love oriented. I am aware there are strains that feel like a sergeant kicking your ass in a boot camp. And also different strains of Caapi definitely should have a variety of characters also.
The consciousness of plants is a constant source of information for medicine, alimentation, and art, and an example of the intelligence and creative imagination of nature. Much of my education I owe to the intelligence of these great teachers. Thus I consider myself to be the “representative” of plants, and for this reason I assert that if they cut down the trees and burn what’s left of the rainforests, it is the same as burning a whole library of books without ever having read them.
~ Pablo Amaringo