Regarding the calculation of binding energy of molecular absorption on graphene, for which this has been discussed before, the process of calculating $E_{AB}$ is fairly straight forward, i.e., it is the single point energy of the relaxed complex AB. However, the calculation of $E_A$ and $E_B$ can be done in two ways:
Just extract A and B structures from the optimized structure of AB complex and calculate the single point energy of them.
Relax the extracted A and B structures (from the optimized AB complex) again and then calculate the single point energy of them.
Among these two methods, which method is more recommendable to use and why?