When selecting a head, one wants to pair the legs with a head that will not compromise the stiffness of the system as a whole. On the other hand, a head that is too big adds diminishing performance increases and just adds weight.
Below is the optimization result for selecting a ball head. This chart plots the stiffness to weight ratio for this tripod and each ball head that I have tested in blue dots versus the stiffness of those heads. The red line is a generalized model for a strong performing ball head. The higher up on the this graph the higher stiffness/weight performance of the system. More information on this analysis can be found in the ball head choice optimization page.
This chart is telling us ….
Note that these recommendations are limited to the tripod heads I have tested. The more general discussion above should provide adequate guidance if your head of choice is not listed.