That depends on how much focus you wanna give to the singular title.
Cause when you make a custom, regardless of the number of cores inside, that title is considered one title, meaning that the other sub in your stack is gonna occupy the same amount of information (assuming you use both at full loops), so the expression of the singular title will be more perceivable than the joint effect of the cores in the custom.
So you could potentially end up with a genius Khan custom, and WANTED (as a single title) will add on to make that genius Khan more physically attractive.
Cores in a custom come mixed together from the Q-Store, while stacking allows you to mix subs consciously.