Dense plasma foci and deuterium gas puff Z-pinches are studied as sources of fusion neutrons. To design a neutron-optimized plasma focus, the drive parameter has been discussed in the last 15 years. Here, , , and represent the peak discharge current, the inner electrode radius, and the initial gas density, respectively. In this paper, similarities between a dense plasma focus and a gas puff Z-pinch are shown. The drive parameter of dense plasma foci seems to be closely related to the parameter of Z-pinches, where and stand for the current during stagnation and linear mass, respectively. On the 3-MA Z-pinch generator, it was found that the optimal parameter reached the value of about . This optimal value can be explained by a tradeoff between the energy of fast deuterons and the number of fast and target deuterons. Obtained experimental results show that the optimal drive parameter cannot be fully explained without the consideration of ion acceleration mechanisms to fusion energies.