This study parametrically examines the implications on inertial fusion reactor design of the use of direct drive pellets as an alternative to the radiation-driven targets. We have examined the impacts of direct illumination on mirror damage constraints, reactor neutronic performance, and system energetics and cost. The capital costs for low f/number, direct-illumination-driven inertial fusion power plants are required to be significantly less than those for the radiation-driven or high f/number direct illumination driven power plants to produce electricity at the same cost.